Android: If you have a tendency to sleep through alarms, Walk Me Up can help you by forcing you to get out of bed and move around. The app uses your phone's accelerometer to count the number of steps you take after the alarm goes off.
If you try to accelerate the process by shaking your phone, the counter resets. You can also set the alarm to vibrate, although the app will warn you that this could interfere with the step count, depending on your phone.
Walk Me Up! Alarm Clock (free) [Google Play]