Android: If you have a new Samsung Galaxy Note II (like I do) you probably enjoy Smart Rotation, a feature that rotates your display based on where the front-facing camera detects your face instead of using the accelerometer. Now any Android user can have this option with GMD Smart Rotate.
The app can also keep your screen from turning off while you're looking at the display, force rotations on applications you normally cannot, and in the pro version you can specify which apps should and should not rotate.
It is that last feature that is causing me to consider paying the modest $1.93 for the pro unlock key even though the other features already exist in my Galaxy Note II. Non-Galaxy owners should definitely consider the app.