I've got a Samsung Smart Watch, which is meant to be able to track sleep cycles, although I've heard some skeptical reviews from people who should know. Anyway. It should be quite possible to devise an app so that the watch vibrates or buzzes to wake the user, just as they are coming out of a REM cycle (or perhaps at other points, depending on needs).

This seems like such an obvious idea that I'm sure someone has done it.

Does anyone know of anything like that out there? Can anyone make any recommendations?

Thanks for anything anyone can offer.