Three Norwegians have built a WiFi measuring rod in order to "visualize the immaterial networks found within cities". As they move around with the 4 metre rod, the 80 LEDs that run its length pulsate based on the strength of a selected WiFi signal. Through time-lapse photography, the pulsing lights create a physical representation of how different types of networks behave in their specific environments. See more photos on the designboom website
, as well as more details on the people and the philosophy behind this.