Household radar can sense a person’s breathing and heart rate, even emotions

Using radio waves to detect what’s on the other side of a wall has been done before, but with sophisticated radar equipment and expensive antenna arrays. Elliptical Reasoning About Location

The time needed for a radio signal to travel from a transmitting antenna to a reflective object (here, a person) and back to a receiving antenna can be used to constrain the position of that object. Those measurements showed the amount of time it took for a radio signal to leave the transmitter, reach the person in the next room, and reflect back to the receiver—typically several tens of nanoseconds.

Source: spectrum.ieee.org