I actually paid about $300 for an alarm clock several years ago that has you wear a head-band that monitors your sleep cycles. You tell it what time you want to wake up in the morning, and for 30 min before that time - if it sees you come out of REM/deep-sleep into light sleep, it will wake you up then. Its really nice, although I don't use it all that often because the head-band is kind of annoying.
Yeah, there are better ways of achieving the same thing. Mainly through apps. You don't have to wear a headband or anything. You can try it :D
That's an interesting gadget. Too bad it's not comfortable!