Levelizer vibrates your phone when you're taking a crooked photo.

Can't see your screen in the sun or holding it at an odd angle? Keep turning it until it stops vibrating and you'll know your picture is straight!
Use your favorite camera; Levelizer runs in the background. Your phone will give you gentle taps until you're holding it more or less level.

This app uses Accessibility services to detect when your camera is launched.
Supports Android Jelly Bean 4.1 and later.