iOS/Android: We sleep in cycles, and you can feel completely groggy or fully rested depending on where you are in the cycle when you wake up. Smart Alarm Clock tracks your sleep cycles and wakes you up at just the right time.
After downloading the free app, you simply select a time range of when you want to wake up (for example, 7:00-7:30AM). Once this alarm is set, the app will record your movements and sounds if you keep it next to you. From there, it will track your cycle and wake you up during your lightest sleep phase in the range you've selected.
Obviously, in order for the app to work, you have to be OK with granting it access to record this data. It's sort of like the previously mentioned Sleepyti.me, but in app form. It also plays soothing sounds to lull you to sleep and, since it records your sleep, you can find out if you snore. To check it out for yourself, head to the links below.
Smart Alarm Clock [Apple Store]
Smart Alarm Clock [Google Play]