Add watch function for battery level

infinitime.go

@@ -351,6 +351,34 @@ func (i *Device) WatchHeartRate() (<-chan uint8, error) {
 	return out, nil
 }
 
+func (i *Device) WatchBatteryLevel() (<-chan uint8, error) {
+	if !i.device.Properties.Connected {
+		return make(<-chan uint8), nil
+	}
+	// Start notifications on heart rate characteristic
+	err := i.battLevelChar.StartNotify()
+	if err != nil {
+		return nil, err
+	}
+	// Watch characteristics of heart rate characteristic
+	ch, err := i.battLevelChar.WatchProperties()
+	if err != nil {
+		return nil, err
+	}
+	out := make(chan uint8, 2)
+	go func() {
+		// For every event
+		for event := range ch {
+			// If value changed
+			if event.Name == "Value" {
+				// Send heart rate to channel
+				out <- uint8(event.Value.([]byte)[0])
+			}
+		}
+	}()
+	return out, nil
+}
+
 // SetTime sets the watch's time using the Current Time Service
 func (i *Device) SetTime(t time.Time) error {
 	if !i.device.Properties.Connected {