No, this isn't some concept, but rather a real system developed by MIT researchers. It basically consists of three radio antennas, spread apart by a meter, aimed at a wall. According to Dvice, "Two of the antennas transmit radio waves, while one receives them. The waves reflect off a human body in the other room, and the receiving antenna grabs those reflections and feeds the data into the computer, which uses it to find the person in question." Continue reading for a video and more information.
Here's what MIT Ph.D candidate Fadel Adlib has to say:
What we're doing here is localization through a wall without requiring you to hold any transmitter or receiver [and] simply by using reflections off a human body.
What is impressive is that our accuracy is higher than even state of the art Wi-Fi localization.