via Jamie Lawrence:

The Seamful Game is a GPS and WiFi based game played in the streets using PDAs. It began life as a project to test an idea about exploiting and exploring the seams of an 802.11 wireless network. Now approximately one year on, Bill is a fully featured multiplayer team game, which has been accused of being fun to play. Players must develop an understanding of the network coverage and the effect of signal strength in order to successfully play the game. In this way we are turning the patchy network coverage, which is usually seen as a problem to be overcome, or worse ignored, into a feature (indeed possibly the main feature) of the game.