This is an excellent idea! Three Scandinavian guys, Timo Arnall, Jørn Knutsen and Einar Sneve Martinussen managed to "reveal" the immaterial landscape of the WiFi networks around the city. What they did is brilliant. They made a pole with an LED array. An Arduino board (probably with the WiFly shield) measures the strength of the network and lights the LEDs accordingly, similar to the VU meters. A guy then walks with the pole in front of a camera set into long exposure time. The result is absolutely amazing. Watch the following video.