diff --git a/.swiftformat b/.swiftformat
index d812125..b7d8e75 100644
--- a/.swiftformat
+++ b/.swiftformat
@@ -2,7 +2,8 @@
 --indent 2
 --ifdef indent
 --trimwhitespace always
---wraparguments preserve
+--wraparguments before-first
+--wrapparameters before-first
 --wrapcollections preserve
 --wrapconditions after-first
 --typeblanklines preserve
diff --git a/Sources/ClientLive/AsyncClient.swift b/Sources/ClientLive/AsyncClient.swift
new file mode 100644
index 0000000..396dcae
--- /dev/null
+++ b/Sources/ClientLive/AsyncClient.swift
@@ -0,0 +1,226 @@
+import EnvVars
+import Logging
+import Models
+import MQTTNIO
+import NIO
+import Psychrometrics
+
+public class AsyncClient {
+
+  public static let eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+  public let client: MQTTClient
+  public private(set) var shuttingDown: Bool
+  public private(set) var sensors: [TemperatureAndHumiditySensor]
+
+  var logger: Logger { client.logger }
+
+  public init(
+    envVars: EnvVars,
+    logger: Logger,
+    sensors: [TemperatureAndHumiditySensor] = []
+  ) {
+    let config = MQTTClient.Configuration(
+      version: .v3_1_1,
+      userName: envVars.userName,
+      password: envVars.password,
+      useSSL: false,
+      useWebSockets: false,
+      tlsConfiguration: nil,
+      webSocketURLPath: nil
+    )
+    self.client = MQTTClient(
+      host: envVars.host,
+      identifier: envVars.identifier,
+      eventLoopGroupProvider: .shared(Self.eventLoopGroup),
+      logger: logger,
+      configuration: config
+    )
+    self.shuttingDown = false
+    self.sensors = sensors
+  }
+
+  public func addSensor(_ sensor: TemperatureAndHumiditySensor) throws {
+    guard sensors.firstIndex(where: { $0.location == sensor.location }) == nil else {
+      throw SensorExists()
+    }
+    sensors.append(sensor)
+  }
+
+  public func connect() async {
+    do {
+      try await client.connect()
+      client.addCloseListener(named: "AsyncClient") { [self] _ in
+        guard !self.shuttingDown else { return }
+        Task {
+          self.logger.debug("Connection closed.")
+          self.logger.debug("Reconnecting...")
+          await self.connect()
+        }
+      }
+      logger.debug("Connection successful.")
+    } catch {
+      logger.trace("Connection Failed.\n\(error)")
+    }
+  }
+
+  public func shutdown() async {
+    shuttingDown = true
+    try? await client.disconnect()
+    try? await client.shutdown()
+  }
+
+  /// Subscribe to changes of the temperature and humidity sensors.
+  func subscribeToSensors(qos: MQTTQoS = .exactlyOnce) async throws {
+    for sensor in sensors {
+      try await client.subscribeToSensor(sensor, qos: qos)
+    }
+  }
+
+  func addSensorListeners(qos: MQTTQoS = .exactlyOnce) async throws {
+    for sensor in sensors {
+      try await client.subscribeToSensor(sensor, qos: qos)
+      let listener = client.createPublishListener()
+      for await result in listener {
+        switch result {
+        case let .success(value):
+          var buffer = value.payload
+          let topic = value.topicName
+          logger.debug("Received new value for topic: \(topic)")
+
+          if topic.contains("temperature") {
+            // Decode and update the temperature value
+            guard let temperature = Temperature(buffer: &buffer) else {
+              logger.debug("Failed to decode temperature from buffer: \(buffer)")
+              throw DecodingError()
+            }
+            try sensors.update(topic: topic, keyPath: \.temperature, with: temperature)
+
+          } else if topic.contains("humidity") {
+            // Decode and update the temperature value
+            guard let humidity = RelativeHumidity(buffer: &buffer) else {
+              logger.debug("Failed to decode humidity from buffer: \(buffer)")
+              throw DecodingError()
+            }
+            try sensors.update(topic: topic, keyPath: \.humidity, with: humidity)
+
+          } else {
+            let message = """
+            Unexpected value for topic: \(topic)
+            Expected to contain either 'temperature' or 'humidity'
+            """
+            logger.debug("\(message)")
+          }
+
+          // TODO: Publish dew-point & enthalpy if needed.
+
+        case let .failure(error):
+          logger.trace("Error:\n\(error)")
+          throw error
+        }
+      }
+    }
+  }
+
+  // Need to save the recieved values somewhere.
+  // TODO: Remove.
+  func addPublishListener<T>(
+    topic: String,
+    decoding _: T.Type
+  ) async throws where T: BufferInitalizable {
+    _ = try await client.subscribe(to: [.init(topicFilter: topic, qos: .atLeastOnce)])
+    Task {
+      let listener = self.client.createPublishListener()
+      for await result in listener {
+        switch result {
+        case let .success(packet):
+          var buffer = packet.payload
+          guard let value = T(buffer: &buffer) else {
+            logger.debug("Could not decode buffer: \(buffer)")
+            return
+          }
+          logger.debug("Recieved value: \(value)")
+        case let .failure(error):
+          logger.trace("Error:\n\(error)")
+        }
+      }
+    }
+  }
+
+  private func publish(string: String, to topic: String) async throws {
+    try await client.publish(
+      to: topic,
+      payload: ByteBufferAllocator().buffer(string: string),
+      qos: .atLeastOnce
+    )
+  }
+
+  private func publish(double: Double, to topic: String) async throws {
+    let rounded = round(double * 100) / 100
+    try await publish(string: "\(rounded)", to: topic)
+  }
+
+  func publishDewPoint(_ request: Client.SensorPublishRequest) async throws {
+    // fix
+    guard let (dewPoint, topic) = request.dewPointData(topics: .init(), units: nil) else { return }
+    try await publish(double: dewPoint.rawValue, to: topic)
+    logger.debug("Published dewpoint: \(dewPoint.rawValue), to: \(topic)")
+  }
+
+  func publishEnthalpy(_ request: Client.SensorPublishRequest) async throws {
+    // fix
+    guard let (enthalpy, topic) = request.enthalpyData(altitude: .seaLevel, topics: .init(), units: nil) else { return }
+    try await publish(double: enthalpy.rawValue, to: topic)
+    logger.debug("Publihsed enthalpy: \(enthalpy.rawValue), to: \(topic)")
+  }
+
+  public func publishSensor(_ request: Client.SensorPublishRequest) async throws {
+    try await publishDewPoint(request)
+    try await publishEnthalpy(request)
+  }
+}
+
+// MARK: - Helpers
+
+private extension MQTTClient {
+
+  func subscribeToSensor(
+    _ sensor: TemperatureAndHumiditySensor,
+    qos: MQTTQoS = .exactlyOnce
+  ) async throws {
+    do {
+      _ = try await subscribe(to: [
+        MQTTSubscribeInfo(topicFilter: sensor.topics.temperature, qos: qos),
+        MQTTSubscribeInfo(topicFilter: sensor.topics.humidity, qos: qos)
+      ])
+      logger.debug("Subscribed to temperature-humidity sensor: \(sensor.id)")
+    } catch {
+      logger.trace("Failed to subscribe to temperature-humidity sensor: \(sensor.id)")
+      throw error
+    }
+  }
+}
+
+struct DecodingError: Error {}
+struct NotFoundError: Error {}
+struct SensorExists: Error {}
+
+extension TemperatureAndHumiditySensor.Topics {
+  func contains(_ topic: String) -> Bool {
+    temperature == topic || humidity == topic
+  }
+}
+
+extension Array where Element == TemperatureAndHumiditySensor {
+
+  mutating func update<V>(
+    topic: String,
+    keyPath: WritableKeyPath<TemperatureAndHumiditySensor, V>,
+    with value: V
+  ) throws {
+    guard let index = firstIndex(where: { $0.topics.contains(topic) }) else {
+      throw NotFoundError()
+    }
+    self[index][keyPath: keyPath] = value
+  }
+
+}
diff --git a/Sources/ClientLive/Live.swift b/Sources/ClientLive/Live.swift
index 0a80053..068a983 100755
--- a/Sources/ClientLive/Live.swift
+++ b/Sources/ClientLive/Live.swift
@@ -1,15 +1,15 @@
-import Foundation
 @_exported import Client
 import CoreUnitTypes
+import Foundation
 import Models
 import MQTTNIO
 import NIO
 import Psychrometrics
 
-extension Client {
+public extension Client {
 
   // The state passed in here needs to be a class or we get escaping errors in the `addListeners` method.
-  public static func live(
+  static func live(
     client: MQTTNIO.MQTTClient,
     state: State,
     topics: Topics
@@ -34,124 +34,8 @@ extension Client {
       subscribe: {
         // Sensor subscriptions
         client.subscribe(to: .sensors(topics: topics))
-        .map { _ in }
+          .map { _ in }
       }
     )
   }
 }
-
-import Logging
-import EnvVars
-
-public class AsyncClient {
-
-  public static let eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: 1)
-  public let client: MQTTClient
-  public private(set) var shuttingDown: Bool
-
-  var logger: Logger { client.logger }
-
-  public init(envVars: EnvVars, logger: Logger) {
-    let config = MQTTClient.Configuration.init(
-      version: .v3_1_1,
-      userName: envVars.userName,
-      password: envVars.password,
-      useSSL: false,
-      useWebSockets: false,
-      tlsConfiguration: nil,
-      webSocketURLPath: nil
-    )
-    self.client = MQTTClient(
-      host: envVars.host,
-      identifier: envVars.identifier,
-      eventLoopGroupProvider: .shared(Self.eventLoopGroup),
-      logger: logger,
-      configuration: config
-    )
-    self.shuttingDown = false
-  }
-
-  public func connect() async {
-    do {
-      try await self.client.connect()
-      self.client.addCloseListener(named: "AsyncClient") { [self] result in
-        guard !self.shuttingDown else { return }
-        Task {
-          self.logger.debug("Connection closed.")
-          self.logger.debug("Reconnecting...")
-          await self.connect()
-        }
-      }
-      logger.debug("Connection successful.")
-    } catch {
-      logger.trace("Connection Failed.\n\(error)")
-    }
-  }
-
-  public func shutdown() async {
-    self.shuttingDown = true
-    try? await self.client.disconnect()
-    try? await self.client.shutdown()
-  }
-
-  func addSensorListeners() async {
-
-  }
-
-  // Need to save the recieved values somewhere.
-  func addPublishListener<T>(
-    topic: String,
-    decoding: T.Type
-  ) async throws where T: BufferInitalizable {
-    _ = try await self.client.subscribe(to: [.init(topicFilter: topic, qos: .atLeastOnce)])
-    Task {
-      let listener = self.client.createPublishListener()
-      for await result in listener {
-        switch result {
-        case let .success(packet):
-          var buffer = packet.payload
-          guard let value = T.init(buffer: &buffer) else {
-            logger.debug("Could not decode buffer: \(buffer)")
-            return
-          }
-          logger.debug("Recieved value: \(value)")
-        case let .failure(error):
-          logger.trace("Error:\n\(error)")
-        }
-      }
-    }
-  }
-
-
-  private func publish(string: String, to topic: String) async throws {
-    try await self.client.publish(
-      to: topic,
-      payload: ByteBufferAllocator().buffer(string: string),
-      qos: .atLeastOnce
-    )
-  }
-
-  private func publish(double: Double, to topic: String) async throws {
-    let rounded = round(double * 100) / 100
-    try await publish(string: "\(rounded)", to: topic)
-  }
-
-  func publishDewPoint(_ request: Client.SensorPublishRequest) async throws {
-    // fix
-    guard let (dewPoint, topic) = request.dewPointData(topics: .init(), units: nil) else { return }
-    try await self.publish(double: dewPoint.rawValue, to: topic)
-    logger.debug("Published dewpoint: \(dewPoint.rawValue), to: \(topic)")
-  }
-
-  func publishEnthalpy(_ request: Client.SensorPublishRequest) async throws {
-    // fix
-    guard let (enthalpy, topic) = request.enthalpyData(altitude: .seaLevel, topics: .init(), units: nil) else { return }
-    try await self.publish(double: enthalpy.rawValue, to: topic)
-    logger.debug("Publihsed enthalpy: \(enthalpy.rawValue), to: \(topic)")
-  }
-
-  public func publishSensor(_ request: Client.SensorPublishRequest) async throws {
-    try await publishDewPoint(request)
-    try await publishEnthalpy(request)
-  }
-}
diff --git a/Sources/Models/TemperatureAndHumiditySensor.swift b/Sources/Models/TemperatureAndHumiditySensor.swift
index fdd067a..40f071a 100644
--- a/Sources/Models/TemperatureAndHumiditySensor.swift
+++ b/Sources/Models/TemperatureAndHumiditySensor.swift
@@ -3,7 +3,7 @@ import Psychrometrics
 /// Represents a temperature and humidity sensor that can be used to derive
 /// the dew-point temperature and enthalpy values.
 ///
-public struct TemperatureAndHumiditySensor: Equatable, Identifiable {
+public struct TemperatureAndHumiditySensor: Equatable, Hashable, Identifiable {
 
   /// The identifier of the sensor, same as the location.
   public var id: Location { location }
@@ -93,7 +93,7 @@ public struct TemperatureAndHumiditySensor: Equatable, Identifiable {
   }
 
   /// Represents the MQTT topics to listen for updated sensor values on.
-  public struct Topics: Equatable {
+  public struct Topics: Equatable, Hashable {
 
     /// The temperature topic of the sensor.
     public let temperature: String
@@ -111,7 +111,7 @@ public struct TemperatureAndHumiditySensor: Equatable, Identifiable {
 
     init(location: TemperatureAndHumiditySensor.Location) {
       self.temperature = "sensors/\(location.rawValue)/temperature"
-      self.humidity = "sensors/\(location.rawValue)/temperature"
+      self.humidity = "sensors/\(location.rawValue)/humidity"
     }
   }
 }
diff --git a/Sources/Models/TrackedChanges.swift b/Sources/Models/TrackedChanges.swift
index 77f3ca8..e8ac271 100755
--- a/Sources/Models/TrackedChanges.swift
+++ b/Sources/Models/TrackedChanges.swift
@@ -88,3 +88,11 @@ extension TrackedChanges: Equatable where Value: Equatable {
     self.init(wrappedValue: wrappedValue, needsProcessed: needsProcessed, isEqual: ==)
   }
 }
+
+extension TrackedChanges: Hashable where Value: Hashable {
+
+  public func hash(into hasher: inout Hasher) {
+    hasher.combine(wrappedValue)
+    hasher.combine(needsProcessed)
+  }
+}
diff --git a/Tests/ClientTests/AsyncClientTests.swift b/Tests/ClientTests/AsyncClientTests.swift
index 847520a..b6f6a70 100755
--- a/Tests/ClientTests/AsyncClientTests.swift
+++ b/Tests/ClientTests/AsyncClientTests.swift
@@ -45,47 +45,69 @@ final class AsyncClientTests: XCTestCase {
     await client.shutdown()
   }
 
-  func testNewSensorSyntax() async throws {
-    let client = createClient(identifier: "testNewSensorSyntax")
+  func testSensor() async throws {
+    let client = createClient(identifier: "testSensor")
     let mqtt = client.client
-    let receivedPublishInfo = PublishInfoContainer()
-    let payload = ByteBufferAllocator().buffer(string: "75.123")
-    let sensor = TemperatureAndHumiditySensor(location: .return)
-
+    try client.addSensor(.init(location: .mixedAir))
     await client.connect()
 
-    try await mqtt.subscribeToTemperature(sensor: sensor)
+    Task { try await client.addSensorListeners() }
 
-    let listener = mqtt.createPublishListener()
-
-    Task { [receivedPublishInfo] in
-      for await result in listener {
-        switch result {
-        case let .failure(error):
-          XCTFail("\(error)")
-        case let .success(publish):
-          await receivedPublishInfo.addPublishInfo(publish)
-        }
-      }
-    }
-
-    try await mqtt.publish(to: sensor.topics.temperature, payload: payload, qos: .atLeastOnce)
+    try await mqtt.publish(
+      to: "sensors/mixed-air/temperture",
+      payload: ByteBufferAllocator().buffer(string: "75.123"),
+      qos: .atLeastOnce
+    )
 
     try await Task.sleep(for: .seconds(2))
 
-    XCTAssertEqual(receivedPublishInfo.count, 1)
+    XCTAssert(client.sensors.first!.needsProcessed)
+    XCTAssertEqual(client.sensors.first!.temperature, 75.123)
 
-    if let publish = receivedPublishInfo.first {
-      var buffer = publish.payload
-      let string = buffer.readString(length: buffer.readableBytes)
-      XCTAssertEqual(string, "75.123")
-    } else {
-      XCTFail("Did not receive any publish info.")
-    }
-
-    try await mqtt.disconnect()
-    try mqtt.syncShutdownGracefully()
+    await client.shutdown()
   }
+
+//   func testNewSensorSyntax() async throws {
+//     let client = createClient(identifier: "testNewSensorSyntax")
+//     let mqtt = client.client
+//     let receivedPublishInfo = PublishInfoContainer()
+//     let payload = ByteBufferAllocator().buffer(string: "75.123")
+//     let sensor = TemperatureAndHumiditySensor(location: .return)
+//
+//     await client.connect()
+//
+//     try await mqtt.subscribeToTemperature(sensor: sensor)
+//
+//     let listener = mqtt.createPublishListener()
+//
+//     Task { [receivedPublishInfo] in
+//       for await result in listener {
+//         switch result {
+//         case let .failure(error):
+//           XCTFail("\(error)")
+//         case let .success(publish):
+//           await receivedPublishInfo.addPublishInfo(publish)
+//         }
+//       }
+//     }
+//
+//     try await mqtt.publish(to: sensor.topics.temperature, payload: payload, qos: .atLeastOnce)
+//
+//     try await Task.sleep(for: .seconds(2))
+//
+//     XCTAssertEqual(receivedPublishInfo.count, 1)
+//
+//     if let publish = receivedPublishInfo.first {
+//       var buffer = publish.payload
+//       let string = buffer.readString(length: buffer.readableBytes)
+//       XCTAssertEqual(string, "75.123")
+//     } else {
+//       XCTFail("Did not receive any publish info.")
+//     }
+//
+//     try await mqtt.disconnect()
+//     try mqtt.syncShutdownGracefully()
+//   }
 }
 
 // MARK: Helpers for tests, some of these should be able to be removed once the AsyncClient interface is done.