Skeetendo

I've been interested in something like this, and it kinda started from the idea of making a music player that will let you assign different route/city/etc songs when walking down different streets then I thought if there was some sort of clone where you could encounter "pokemon" while walking, and depending where youre walking, that'd be pretty cool.
The game  could track user location population, so rare "pokemon" would appear in less populated areas (almost like the google april fools, but without the 3D AR)
If this was made, i would imagine there would be an issue with nintendo and a C&D letter, so i'm not sure if we could do a (chinese-esque) knockoff, that could easilly be unofficially hacked to become pokemon
Or.... if there was a special emulator made, that could be used in conjunction with the ROM, that would patch a lot of the game (a very lot)
thoughts?