["Wifi Camera," Sjölén, Haque, Somolai-Fischer, 2006] From Picture This — Reinventing The Camera As A Social And Anti-Technological Object by Jonah Brucker-Cohen, The Creators Project:
[...] “Examining the invisible proliferation of wireless networks that are permeating every location we inhabit comes another type of camera that takes images of the signals themselves. The “Wifi-Camera” (2010) by Bengt Sjölén, Adam Somlai Fischer, and Usman Haque is a camera that takes photos of locations that contain wireless transmissions in the way that a traditional camera captures spaces illuminated by visible light. The camera is meant to reveal all of the electromagnetic space that our mobile and portable devices create daily. From their description: “Radio waves at wifi’s wavelength behave similar to light in that they are reflected off almost all solid objects to varying degrees, just as when we see colors we see the light from a light source being reflected off an object into our eyes.” This effect is achieved by pointing a wireless antenna and measuring the signal strength throughout a viewing period to create an overall image…”
