Now, by plugging an EMI sensor into any wall socket, you can read your house’s EM signature — and if you continue to listen, you can detect changes in the signature. Obvious changes occur when a device is switched on or off, but it also turns out that simply moving your hand close to an LCD monitor also alters your house’s EM signature. It might sound a bit unbelievable, that a single finger moving towards an LCD monitor can be detected by a sensor at the other end of the house, but that’s exactly what the University of Washington researchers have accomplished.

via Turning a standard LCD monitor into touchscreen with a $5 wall-mounted sensor | ExtremeTech.