Ha, check out this iPong multi-player game for iphones!
iPong is a variant of Atari’s classic paddle ball game, with a multi-device, multi-player twist. Using some clever trickery, players can actually bounce their ball off of their iPhone’s screen onto the display of another phone. While the game can’t actually detect the proximity of the devices at this point, it does appear to store the exit position of the ball on one screen and transmit that as the entrance point on the adjacent screen.
Video after the jump.