Yeah, it's not hard to overlay a circle of a certain size over a city, say, Salt Lake (no bias, no bias), and change the color from blue to red as the city gets "hotter" with more usage and whatnot. Something like that.
I'm personally really not a fan of "what bars/clubs/restaurants are people at?" apps that give you random information about random people. I'd just really like to know how many people are using android/mobile devices (maybe even the carrier/manufacturer) in a certain area.