Researchers at Carnegie Mellon University developed a method for detecting the three dimensional shape and movements of human bodies in a room, using only WiFi routers. From a report:
To do this, they used DensePose, a system for mapping all of the pixels on the surface of a human body in a photo. DensePose was developed by London-based researchers and Facebook’s AI researchers. From there, according to their recently-uploaded preprint paper published on arXiv, they developed a deep neural network that maps WiFi signals’ phase and amplitude sent and received by routers to coordinates on human bodies. Researchers have been working on “seeing” people without using cameras or expensive LiDAR hardware for years. In 2013, a team of researchers at MIT found a way to use cell phone signals to see through walls; in 2018, another MIT team used WiFi to detect people in another room and translate their movements to walking stick-figures.