Don't freak out or anything, but those wireless signals you bask in everyday could be watching you. Or at least they might, someday, if the work from a group of researchers at the University of Utah makes it beyond the lab. 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. As you might expect, however, that's not quite as simple as a firmware upgrade, and currently requires a 34-node network to keep watch on a standard living room, which is apparently enough to pin down moving objects within a meter or so. To do that, the system essentially bombards the space with an array of wireless signals and keeps watch on any changes in signal strength, building up a "picture" of the room in the process. No promises on a commercial version just yet, but the researchers see plenty of potential for it, and are even talking about a portable, GPS-equipped version that police or emergency responders could use before entering a dangerous area.