It's a standard, location-based check-in service. Except that you're dead.
Deadsquare is the morbidly convenient way for you to keep your friends updated on your whereabouts. Just post a photo of yourself dead, and friends and potential mourners are immediately apprised of your location. You can also unlock made-up badges and mayorships, and then award them to yourself any time you want because, what the hell, you're dead.