As Technology Review's Physics arXiv blog reports, they've devised a means to modify a standard 802.15.4 wireless network (commonly used by home automation services like ZigBee) to actually "see" movement through walls, and with some degree of accuracy, no less.
The thought clearly preoccupies the Daily Telegraph's Neil Tweedie, in a review of the Lucasian Professor of Theoretical Physics' appearance on yesterday's Richard and Judy show.