Thinking about mobile games

Mobile games are interesting precisely because nobody, to the best of my knowledge, has ever created one that takes full advantage of mobile phone technology. Mobile phones allow for peer-to-peer communication, they're portable, most modern ones are outfitted with a decent camera and they can be location-tracked using GPRS systems. So... what kind of game could take advantage of all these things?

I've been mulling over these, trying to think of a suitable game that I could present for the 3rd assignment. I don't think anybody really wants to play a simultaneous multiplayer game over a phone (as evidenced by the Multiplayer on the Run section in this Gamasutra article), but I think not implementing any multiplayer functionality is simply ignoring the key features of mobile phone technology, so perhaps a game that is primarily played single-player, but has a multiplayer component, would work better (I'm thinking something similar to online browser RPG Kingdom of Loathing, or Spore's offline-online gameplay).

I'm also thinking that a lot of people don't really enjoy playing twitch-based games on a phone- after all, a phone's keypad isn't built to play Snake (which was near-impossible to play on certain Nokia models). A gameplay mechanism reminiscent of the Japanese RPG Dragon Quest- which strips down the RPG interface to a beautifully elegant level- is one possible solution. Give players a menu and let them input commands using the different number keys on a phone.

What sort of game emerges from these ideas? An RPG, perhaps, that has players fight through dungeons to get treasure, which they could then sell or trade with other players in a multiplayer marketplace? Extrapolating further, why not combine this with location-specific areas, like dungeons that can only be accessed in specific parts of a city (say, Singapore)? As for cameras, I wonder if it would be possible for a server to overlay data onto a real-life scene as viewed through a phone camera viewfinder? Perhaps a certain building, if seen through a phone camera (or photographed by one), could be displayed as a wizard's tower?

These are just some ideas I'm throwing out and a fantasy RPG setting is by no means a requirement, or even what I'd like to go for. Other technologies I'd be interested in exploring include a game where your phone will alert you to the presence of nearby players and a game involving a heavier use of phone photography- perhaps a database of player faces could be created and taking a photo of another players face would bring up data associated with that player that could then be manipulated? Or a game which allows you to "tag" real-life locations with textual information, which can then be viewed by other players. Of course, such games may be impossible today given the limitations of current phone technology, but since we're not implementing said games, why not ignore those limits?