WiFi "Radar"

Traditional radar detects the location of objects by bouncing radio waves off of them and detecting what bounces back. The same principle can be applied to WiFi signals to track a person’s location, even through walls.

WiFi signals are fairly ubiquitous, thanks to the wide-scale use of devices like wireless routers. And just like conventional radio signals, they change frequency when they reflect off of moving objects, a phenomenon known as Doppler Effect. U.K. engineers recently developed a prototype device that can track these signals. It consists of two antennas – one to monitor the baseline signal of the room and one to sense changing frequencies produced by objects or people on the move. As they move closer, the frequency increases; and as they move further away, the frequency decreases. An on-board computer can then calculate the location within a few feet, along with speed and direction. And because the device itself doesn’t give off any signals, it’s undetectable.

While the security implications of such a system are obvious, the developers say that it could also be adapted for use in hospitals to detect a patient’s breathing more accurately than current methods.