For replacing your old alarm clock
Sleep Cycle wakes you only when you’re in a light sleep cycle, not from REM sleep. When your phone is on your mattress, the app uses the phone’s accelerometer to monitor tossing and turning, then wakes you at an opportune moment.
WakeMeHere is great for commuters who sleep on a bus or train, because the alarm goes off only when you’ve reached a preset destination.
Carrot is “very, very good about annoying you out of bed.” The $3 iOS-only app pesters you with a cutesy song and forces you to complete a random task in order to silence the music.
Nebula Alarm Clock is a soothing Android-only alternative. Each night, a star grows on your phone screen while you sleep, and in the morning you turn off the alarm to add the star to your night sky. Snooze, though, and a supernova will destroy your progress.