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This guide provides practical examples for common Apple Watch app patterns using @capgo/capacitor-watch.

Example 1: Health & Fitness Tracker

Section titled “Example 1: Health & Fitness Tracker”

Sync workout data between watch and phone.

import SwiftUI
import CapgoWatchSDK


struct WorkoutView: View {
    @ObservedObject var connector = WatchConnector.shared
    @State private var heartRate: Double = 0
    @State private var calories: Double = 0
    @State private var isTracking = false


    var body: some View {
        VStack(spacing: 12) {
            // Heart Rate Display
            HStack {
                Image(systemName: "heart.fill")
                    .foregroundColor(.red)
                Text("\(Int(heartRate)) BPM")
                    .font(.title2)
            }


            // Calories
            HStack {
                Image(systemName: "flame.fill")
                    .foregroundColor(.orange)
                Text("\(Int(calories)) cal")
            }


            // Start/Stop Button
            Button(isTracking ? "Stop" : "Start") {
                toggleTracking()
            }
            .buttonStyle(.borderedProminent)
            .tint(isTracking ? .red : .green)
        }
        .onReceive(Timer.publish(every: 1, on: .main, in: .common).autoconnect()) { _ in
            if isTracking {
                updateMetrics()
            }
        }
    }


    private func toggleTracking() {
        isTracking.toggle()
        if isTracking {
            // Notify phone that workout started
            connector.sendMessage([
                "event": "workoutStarted",
                "timestamp": Date().timeIntervalSince1970
            ])
        } else {
            // Send final summary to phone
            do {
                try connector.updateApplicationContext([
                    "workoutComplete": true,
                    "totalCalories": calories,
                    "avgHeartRate": heartRate,
                    "endTime": Date().timeIntervalSince1970
                ])
            } catch {
                print("Failed to update context: \(error)")
            }
        }
    }


    private func updateMetrics() {
        // Simulate heart rate (in real app, use HealthKit)
        heartRate = Double.random(in: 120...160)
        calories += Double.random(in: 0.1...0.3)


        // Send real-time updates if phone is reachable
        if connector.isReachable {
            connector.sendMessage([
                "heartRate": heartRate,
                "calories": calories,
                "timestamp": Date().timeIntervalSince1970
            ])
        }
    }
}

Example 2: Smart Home Remote

Section titled “Example 2: Smart Home Remote”

Control smart home devices from your watch.

import SwiftUI
import CapgoWatchSDK


struct SmartHomeView: View {
    @ObservedObject var connector = WatchConnector.shared
    @State private var devices: [SmartDevice] = []
    @State private var isLoading = false


    var body: some View {
        NavigationView {
            Group {
                if isLoading {
                    ProgressView("Loading...")
                } else if devices.isEmpty {
                    Text("No devices")
                        .foregroundColor(.secondary)
                } else {
                    List(devices) { device in
                        DeviceRow(device: device, onToggle: { toggleDevice(device) })
                    }
                }
            }
            .navigationTitle("Home")
            .toolbar {
                Button(action: refreshDevices) {
                    Image(systemName: "arrow.clockwise")
                }
            }
        }
        .onAppear {
            refreshDevices()
        }
        .onChange(of: connector.lastMessage) { message in
            handleMessage(message)
        }
    }


    private func refreshDevices() {
        guard connector.isReachable else {
            // Load from cached context
            loadFromContext()
            return
        }


        isLoading = true
        connector.sendMessage(["action": "getDevices"]) { reply in
            DispatchQueue.main.async {
                isLoading = false
                if let deviceList = reply["devices"] as? [[String: Any]] {
                    devices = deviceList.compactMap { SmartDevice(from: $0) }
                }
            }
        }
    }


    private func toggleDevice(_ device: SmartDevice) {
        connector.sendMessage([
            "action": "toggleDevice",
            "deviceId": device.id,
            "newState": !device.isOn
        ]) { reply in
            DispatchQueue.main.async {
                if reply["success"] as? Bool == true {
                    // Update local state
                    if let index = devices.firstIndex(where: { $0.id == device.id }) {
                        devices[index].isOn.toggle()
                    }
                }
            }
        }
    }


    private func loadFromContext() {
        if let deviceList = connector.applicationContext["devices"] as? [[String: Any]] {
            devices = deviceList.compactMap { SmartDevice(from: $0) }
        }
    }


    private func handleMessage(_ message: [String: Any]) {
        // Handle push updates from phone
        if let update = message["deviceUpdate"] as? [String: Any],
           let deviceId = update["id"] as? String,
           let isOn = update["isOn"] as? Bool {
            if let index = devices.firstIndex(where: { $0.id == deviceId }) {
                devices[index].isOn = isOn
            }
        }
    }
}


struct SmartDevice: Identifiable {
    let id: String
    let name: String
    let type: String
    var isOn: Bool


    init?(from dict: [String: Any]) {
        guard let id = dict["id"] as? String,
              let name = dict["name"] as? String,
              let type = dict["type"] as? String,
              let isOn = dict["isOn"] as? Bool else {
            return nil
        }
        self.id = id
        self.name = name
        self.type = type
        self.isOn = isOn
    }
}


struct DeviceRow: View {
    let device: SmartDevice
    let onToggle: () -> Void


    var body: some View {
        HStack {
            Image(systemName: iconName)
                .foregroundColor(device.isOn ? .yellow : .gray)
            Text(device.name)
            Spacer()
            Toggle("", isOn: .constant(device.isOn))
                .labelsHidden()
                .onTapGesture { onToggle() }
        }
    }


    var iconName: String {
        switch device.type {
        case "light": return device.isOn ? "lightbulb.fill" : "lightbulb"
        case "thermostat": return "thermometer"
        case "lock": return device.isOn ? "lock.fill" : "lock.open"
        default: return "power"
        }
    }
}

Example 3: Notification Center

Section titled “Example 3: Notification Center”

Send custom notifications to the watch.

import { CapgoWatch } from '@capgo/capacitor-watch';


class NotificationService {
  async sendNotification(title: string, body: string, data?: any) {
    const info = await CapgoWatch.getInfo();


    if (info.isReachable) {
      // Send immediately if watch is reachable
      await CapgoWatch.sendMessage({
        data: {
          type: 'notification',
          title,
          body,
          data,
          timestamp: Date.now()
        }
      });
    } else {
      // Queue for later delivery
      await CapgoWatch.transferUserInfo({
        userInfo: {
          type: 'notification',
          title,
          body,
          data,
          timestamp: Date.now()
        }
      });
    }
  }


  async sendUrgentAlert(message: string) {
    // Use sendMessage for urgent alerts (requires watch to be reachable)
    const info = await CapgoWatch.getInfo();


    if (!info.isReachable) {
      console.warn('Watch not reachable for urgent alert');
      return false;
    }


    await CapgoWatch.sendMessage({
      data: {
        type: 'urgentAlert',
        message,
        haptic: 'warning',
        timestamp: Date.now()
      }
    });


    return true;
  }
}


// Usage
const notifications = new NotificationService();


// Regular notification (queued if watch unavailable)
await notifications.sendNotification(
  'Order Update',
  'Your order has shipped!',
  { orderId: '12345' }
);


// Urgent alert (requires watch to be active)
const sent = await notifications.sendUrgentAlert('Security alert: New login detected');

Example 4: Data Sync Service

Section titled “Example 4: Data Sync Service”

Keep data synchronized between phone and watch.

import { CapgoWatch } from '@capgo/capacitor-watch';


class DataSyncService {
  private syncQueue: any[] = [];
  private isSyncing = false;


  async initialize() {
    // Listen for sync requests from watch
    await CapgoWatch.addListener('messageReceivedWithReply', async (event) => {
      if (event.message.action === 'sync') {
        const data = await this.getDataForSync(event.message.lastSyncTime);
        await CapgoWatch.replyToMessage({
          callbackId: event.callbackId,
          data: { items: data, syncTime: Date.now() }
        });
      }
    });


    // Listen for data from watch
    await CapgoWatch.addListener('userInfoReceived', (event) => {
      this.handleWatchData(event.userInfo);
    });


    // Monitor connectivity for sync opportunities
    await CapgoWatch.addListener('reachabilityChanged', (event) => {
      if (event.isReachable && this.syncQueue.length > 0) {
        this.processSyncQueue();
      }
    });
  }


  // Push important data to watch (guaranteed delivery)
  async pushToWatch(data: any) {
    await CapgoWatch.transferUserInfo({
      userInfo: {
        type: 'dataUpdate',
        data,
        timestamp: Date.now()
      }
    });
  }


  // Update shared state (latest value only)
  async updateSharedState(state: any) {
    await CapgoWatch.updateApplicationContext({
      context: {
        ...state,
        lastUpdated: Date.now()
      }
    });
  }


  // Queue data for sync when watch becomes available
  queueForSync(data: any) {
    this.syncQueue.push(data);
    this.attemptSync();
  }


  private async attemptSync() {
    const info = await CapgoWatch.getInfo();
    if (info.isReachable) {
      await this.processSyncQueue();
    }
  }


  private async processSyncQueue() {
    if (this.isSyncing || this.syncQueue.length === 0) return;


    this.isSyncing = true;


    while (this.syncQueue.length > 0) {
      const item = this.syncQueue.shift();
      await CapgoWatch.transferUserInfo({ userInfo: item });
    }


    this.isSyncing = false;
  }


  private async getDataForSync(lastSyncTime: number): Promise<any[]> {
    // Return data modified since lastSyncTime
    // This would query your database/API
    return [];
  }


  private handleWatchData(data: any) {
    console.log('Received from watch:', data);
    // Process and save data from watch
  }
}

Best Practices

Section titled “Best Practices”

1. Choose the Right Transfer Method

Section titled “1. Choose the Right Transfer Method”
MethodUse CaseDelivery
sendMessageInteractive, time-sensitiveImmediate (fails if unreachable)
updateApplicationContextCurrent app stateLatest value only
transferUserInfoImportant dataQueued, guaranteed

2. Handle Offline Gracefully

Section titled “2. Handle Offline Gracefully”
async function smartSend(data: any, important: boolean) {
  const info = await CapgoWatch.getInfo();


  if (info.isReachable) {
    // Send immediately
    await CapgoWatch.sendMessage({ data });
  } else if (important) {
    // Queue for later
    await CapgoWatch.transferUserInfo({ userInfo: data });
  } else {
    // Update context (will be available when watch opens app)
    await CapgoWatch.updateApplicationContext({ context: data });
  }
}

3. Minimize Data Size

Section titled “3. Minimize Data Size”
// Bad - sending large objects
connector.sendMessage(["user": fullUserObject])


// Good - send only what's needed
connector.sendMessage([
    "userId": user.id,
    "name": user.displayName,
    "avatarUrl": user.avatarUrl
])

4. Use Haptics Appropriately

Section titled “4. Use Haptics Appropriately”
import WatchKit


// Success feedback
WKInterfaceDevice.current().play(.success)


// Failure feedback
WKInterfaceDevice.current().play(.failure)


// Navigation feedback
WKInterfaceDevice.current().play(.click)


// Notification
WKInterfaceDevice.current().play(.notification)

5. Cache on Watch

Section titled “5. Cache on Watch”
class DataCache {
    private let defaults = UserDefaults.standard


    func save(_ data: [String: Any], forKey key: String) {
        if let encoded = try? JSONSerialization.data(withJSONObject: data) {
            defaults.set(encoded, forKey: key)
        }
    }


    func load(forKey key: String) -> [String: Any]? {
        guard let data = defaults.data(forKey: key),
              let dict = try? JSONSerialization.jsonObject(with: data) as? [String: Any] else {
            return nil
        }
        return dict
    }
}

Next Steps

Section titled “Next Steps”

Keep going from Examples & Use Cases

Section titled “Keep going from Examples & Use Cases”

If you are using Examples & Use Cases to plan native plugin work, connect it with Using @capgo/capacitor-watch for the native capability in Using @capgo/capacitor-watch, Capgo Plugin Directory for the product workflow in Capgo Plugin Directory, Capacitor Plugins by Capgo for the implementation detail in Capacitor Plugins by Capgo, Adding or Updating Plugins for the implementation detail in Adding or Updating Plugins, and Ionic Enterprise Plugin Alternatives for the product workflow in Ionic Enterprise Plugin Alternatives.