How about an MMO game for camera phones like iPhone4 and others where the game client connects to a central MMO-like server to populate the real world with robot AIs that can only be viewed when looking through your phone cam. These robot ghosts could be interactive through the phone controls and could have memory, be robotic or humanoid, alien, with plots and quests and acheivements for meeting them and whatnot, and might interact physically with 3d things in real world but not actually able to touch or move anything, of course. Maybe some player interaction via the robot ghosts and other mechanisms also.

I thought of a pokemon style game (having not actually played it), where you as a player get an alert when a mmo pokemonster is nearby, then you photograph it for points with your phonecam or 3ds cam. The 3ds cams can do the kinect tracking trick, so this might make a good 3ds game, then model the location abstractly unless a player is nearby running their camera, then use that camera to draw a map for the AI model to interact with. A public leaderboard might be fun too, along with letting players have their pokemons fight over wireless. The leaderboard might also show the picture of capped pokemons, along with a physical route log that is posted on capture/deletion. Make spawns pretty frequent and near players and a bit random. Possibly make each one slightly unique, like the mmo-character makers.

A non-mmo game might be where the player maps out their house with a 3ds, making a bounding box or shape. Then they spawn one or more ai 'bad guys', zombies or whatever, with or without guns (mostly with), then aim at them with the 3ds and push a button to fire a virtual gun at the virtual character in the actual environment. Maybe build a gun-shaped controller just for this or attachment too.

I like the 3ds pokemon idea. I could see nintendo already thinking that up. Augmented reality pokemon using the 3d camera. And going head to head with others. Uh oh, just thought of rare pokemons being faught over while players are at school. I wonder if those 3ds have gps, they could make it so that pokemon do not appear around schools. Oh jeez the possibilites are endless with a pokemon