I'm interested in using Apple Watch for sleep studies. This requires collecting data from accelerometer and potentially heart rate sensor over extended periods of time.
Does watchOS2 allow me as a developer to run an app in the foreground until the battery runs out?
Or will the watchOS force my app to become suspended as a result of wrist gestures or timeout?
There is currently no legitimate way to prevent the watch from going to sleep.
Your app would, presumably, also need methods to prevent the side button and crown from performing their default functions, and such methods do not exist.