Georgia Tech's Mobile Technologies Group announced that they have developed a collection of games for mobile phones that require physical gesture interactions. User can play these games by moving the handset itself in free space. The gesture-based games use the cellphone's camera as a motion detector. Up to 6 degrees of freedom can be detected by using computer vision techniques, such as motion blur detection and optical flow. Three prototype games have been developed - a single player Pong game and a multiplayer version of the Pong game that involve moving the whole phone to the left and right, as well as a Doodle game that according to the developers' words demonstrates the various degrees of freedom.
Source: Georgia Tech