I need to get accelerometer and gyroscope data from an Android Wear device to an Android phone.
It would be preferable if the Android Wear does not have an app installed (or at least an app with no UI; i.e. a Service), and if there is some provision in any of the Android SDKs or Play Services libraries to simply connected from an Android phone to an already-paired Wear device, and log sensor data.
Whatever I've read up till now points me towards installing an app on the Wear, and then going through the route of sending a message from the phone to the wear, and then receiving a stream of messages from it. On sending another message to stop, the wear will in turn stop the stream of messages.
Is this the only way to approach the task, or is there an easier way provided within the Wear SDK or any other SDK?
You can't access watch sensor data from phone without an app of your own running on the watch. A Service will be fine, if you don't need a watch UI - but you will need to write this piece yourself, and use the Wear Data API to move/synchronize data between the phone and watch.