Maybe we do need that foil hat after all because, according to the Daily Telegraph the University of Utah in the United States has been using WiFi signals to see through walls. At the moment their equipment can only see approximately three feet the other side of the wall but they are confident they can extend both the range and resolution of the system to make it a useful tool for Police, military and security personnel involved in surveillance. The images produced are similar to those seen on sonar and the system works like sonar or radar by picking up variations in the signal pattens. The developers foresee a set of receiving sensors being dropped off around a building under siege allowing a 3D representation of the whereabouts of people within the building to be accessed. All okay unless the rooms have been painted with the magic RF proof paint mentioned below or someone has turned off the WiFi. Just how is this any better than the infra-red systems already on sale and in use is a question as yet unanswered.
Read the Telegraph article here
Image borrowed from http://surrealiststreetgang.com/