Source: http://lifehacker.com/#!5760593/sleep-as-a-droid-wakes-you-up-gently-at-your-best-time
Android: You're the mayor of New York, you have super powers, this donut tastes incredible, and then, then—the terrible, awful digital rooster sound. Wake up easier, and with better timing, with this clever customized Android alarm app.
Sleep as an Droid ("Sleep as an Android"—get it?) this app has soothing sounds to wake up to, that can fade in gradually—a nice feature, in itself. But the real benefit of Sleep as an Droid is keeping it on your mattress, so it can measure your movements and get a sense of your sleep cycles. It also logs your sleeping hours, so you can see just how far you're falling behind in the quest for a good night's rest.
With that movement analysis in place, the Sleep app suggests better wake-up times from the data it collects. This might not work for everyone, but you've got 14 days to try it out for free, before you'd need to pony up a small $1.34 (currently) for the unlocked version.