I have been mulling the latest multitouch patents aapl has filed, and an undiscovered interface occurred to me. Why not tap the sides of the device in a pattern such as a double click to activate system-wide features? The accelerometer can pick up a directional impact from what I understand, so why not pretend you have buttons on the surrounding surfaces! My fist thought was double tap the right side to indicate a copy command, then use a different side or input to indicate paste? You might also use it as a sort of limited case 'option' modifier to allow the re-use of gestures... Just brainstorming.