Surveillance device uses Wi-Fi to see through walls

http://www.flickr.com/photos/mm/377784715/

Researchers in England have created a prototype surveillance device that can be used to spy on people inside buildings and behind walls by tracking the frequency changes as Wi-Fi signals generated by wireless routers and access points bounce off people as they move around.

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Story added 21. August 2012, content source with full text you can find at link above.