My new (free) iPad game is out, pls have a look if you like (and have an iPad*):
http://www.youtube.com/watch?v=jLJtTBx2jsY
http://versuspad.com/city-bucks/screenshot-1-medium.jpg

*for what it's worth, it's all JavaScript, so as soon as other tablet hardware becomes popular and has similar capabilities, I plan to release it for other platforms too :)

Another requirement: you need a friend to play with.

True. All the games I'm doing right now are exclusively two-(or more)-player.