Want to claim your city as your own? Competing with a rival gang for turf, and want to avoid messy knife fights? Well now you can, thanks to Urban Defender. Working over a short time period, a team of students from Zurich University of Arts built a system to claim buildings by throwing a specially equipped ball at them. Impacts are detected by an accelerometer connected to an Arduino, which is wirelessly connected to a Beagle board which uses a GPS to coordinate the hit to a specific address.

They apparently didn’t have time to finish the multi-player version of the game, but I think the concept is too good to let die. Someone should definitely hook this up to the social networking game foursquare. As a bonus, you could use the sensor units to play the actual game four square when you get tired of fighting for turf.