CamBlaster! is a game which can only be played on a cameraphone. It provides moving targets that the player can "shoot" while moving the camera around. The site's a little vague on how this is accomplished, but presumably the software looks for changes in what the camera sees and figures out direction and speed of movement. It is even able to keep track of how far the camera has moved, and can put the same targets back where they (apparently) were when the camera moves back to its original position.
Don't think of it as a game; think of it as an early-indicator, and think about how it might combine with other mobile phone technologies. Take the (horribly named) "crunkies" idea I posted about last week, a system for planting location-based messages, "tagging" the space. Adding in the ability to gauge roughly what direction the camera is facing (with the "origin" set by pointing it at a given item) would allow for a more complex set of tags, with different SMS messages coming in depending upon where the cameraphone was pointed. Or add the animations to some kind of barcode reading system for the cameraphone, so that icons for the results could be shown over the item and remain tagged in place even when the cameraphone is moved around.
This gets really interesting when you start adding in heads-up displays...