Just as cheap, accurate GPS facilitated geocaching, unlimited calling cellphone plans are allowing for the creation of urban spatial games. Of course they'll remain crude until phones can automatically determine their location and transmit it in machine-readable format, but I think there may even be a business-model somewhere in here, so it's a trend to watch.

(The classic game (which supposedly even got passed-off as a research project) is PacManhattan, but this one is CanCon and created by a second-order friend, so it's better.)