Remember me mentioning the special paint for making wi-fi cold-spots?

Well, here’s a reason you might want to invest in some – via Bruce Schneier we discover that some folk at the University of Utah have found a way to surveil the inside of a building using wireless signals:

The surveillance technique is called variance-based radio tomographic imaging and works by visualizing variations in radio waves as they travel to nodes in a wireless network. A person moving inside a building will cause the waves to vary in that location, the researchers found, allowing an observer to map their position.

The researchers, electrical engineering graduate student Joey Wilson and his faculty advisor Neil Patwari, have tested the technique with a 34-node wireless network using the IEEE 802.15.4 wireless protocol, according to the MIT Technology Review. By “interrogating” the space with signals and multiple receivers, the researchers found they were able to read the waves to detect the location of a moving object within a meter of accuracy.

OK, so it’s not quite kit you can buy from the local Electronics Barn… but you can pretty much guarantee that now the proof-of-concept has been done, all sorts of smart types will be looking at making affordable homebrew versions. [image by delta_avi_delta]