This looks pretty rad - modulo the normal qualm of sharing all your location data with google, of course. I've been fiddling around with a lot of ideas for geolocated X on mobile (local chat, virtual graffiti, flashmob coordinators, etc) and the infrastructure to decide who is where is a bit heavy. Farming that to google at least for the MVP stage seems like a reasonable decision. Then, if we decide that google's tracking is a significant barrier to user adoption, we can roll our own once we're happy with how it's going.
