SCVNGR (think scavenger) is a social check in game all about going places.  HEre's a hands-on video shwoing off some of the cool functionality on iPhone

Available on iPhone and Android mobile clients and there’s also developer tools available for those who want to build on the platform. See scvngr.com. Users can enjoy a fun, social gaming experience, share details via facebook and Twitter, snap and include photos, go on a scavenger hunt, create a game, and much more. Photo - Ok social checkin fans I’m calling it, watch out for #scvngr …