I\'m using the Data API in a service for Android Wear in a watch face that pulls down data from the cloud in a phone app and syncs it through a DataMap to the paired watch a
While having separate service could definitely fit the bill, I was researching for possibly having just one service for both CanvasWatchFaceService and being registered for Data Layers API, and seems the DigitalWatchFaceService in the Google sample/android-WatchFace provide an example of this.
Notice it provide example to register both as BroadcastReceiver AND the Data API.
Hope this helps.
https://github.com/googlesamples/android-WatchFace/blob/master/Wearable/src/main/java/com/example/android/wearable/watchface/DigitalWatchFaceService.java