Apple had a 2006 patent related to operating, to a certain extent, a device using gestures and touches on its back and a recent Google patent might bring that concept to future Android phones. The principle is as easy as touching the back casing of the Android device in order to interact with the gadget.
Non-touchscreen contact on the rear of the device could be detected if the this patent ever gets implemented. Daily usage scenarios include turning a page in a document, skipping to a next picture in a slideshow or even advancing to the next track in a playlist. Feedback for registering the back-tap could be either visual, acoustic, or tactile and the implementation might also make its way to tablets.
Whether this is something we’ll soon see in Android devices is yet unknown, as there’s a long road from patent applications to actual implementation, but it could bring a new, innovative way we interact with our devices.