Wi-Fi That Sees Through Walls (http://www.informationweek.com/mobility/smart-phones/wi-fi-that-sees-through-walls/240157566)
Thomas Claburn, Information Week | 29 June 2013

Researchers at MIT’s Computer Science and Artificial Intelligence Laboratory have come up with a way to create a low-power, portable device that can see through walls using Wi-Fi signals.

Technology of this sort, similar in concept to radar or sonar, has existed for years . . .