Your TV can see through walls:

A simple software-defined radio receiving an ordinary ATSC digital TV broadcast can detect and measure human motion through walls, according to a demonstration by an engineer using an Ettus USRP B200 receiver. The setup exploits selective fading, in which a strong reflection cancels the direct signal, leaving the residual extremely sensitive to nearby movement; walking in an adjacent room produced clear striping in the signal waterfall. By measuring the roughly 70-pixel gap between stripes at a 150 Hz update rate, the author calculated a walking speed of about 2.1 Hz, or 1.3 meters per second (4.6 km/h), with no geometry correction needed because the motion was perpendicular to the signal path. The result matters because it shows that any wideband radio signal, including WiFi and LTE, can serve as a motion sensor without dedicated hardware, though those signals produce messier waterfalls that require more processing to extract the same data. What to watch next is whether consumer devices begin tapping ambient broadcast and network signals for through-wall sensing, turning existing radio infrastructure into a ubiquitous motion-detection layer.