Anyone knows a good app to wake up when you are at the lightest in your sleep stages? I only found 2: Sleepbot and Sleep as Android. Just yesterday I tried Sleepbot but it seems it's a gimmick. It literally wakes you up when you move in bed noticeably during your set "sleep tracking" timeframe. Obviously that doesn't mean I was ready to wake up.

I remember trying something on iOS before I sold my ipod but I forgot. I thought it kinda worked but can't remember.

What do you recommend? Are these useless gimmicks or are there apps based on sound scientific principles?