New artificial intelligence technology developed at MIT can see through walls, and it knows what you’re doing.

RF-Pose, created by researchers at the Computer Science and Artificial Intelligence Laboratory (CSAIL), uses wireless signals to estimate a person’s pose through a wall. It can only come up with a 2D stick figure of your movements, but it can nonetheless see your actions.

The system, described in a new paper [PDF], uses a neural network to piece together radio signals bouncing off the human body. It takes advantage of the fact that the body reflects radio frequency signals in the Wi-Fi range. These Wi-Fi signals can move through walls, but not through people.

Using data from low-power radio signals—1000 times lower than the power your home Wi-Fi router puts out—this algorithm can generate a relatively accurate picture of what the person behind the wall is doing by piecing together the signals reflected by the moving body.

The system can recognize movement in poor lighting and identify multiple different individuals in a scene. Though the technology is still in development, it’s not hard to imagine that the military might use it in surveillance, but the researchers also suggest that it may be useful for video game design and search-and-rescue missions. It might also help doctors monitor and analyze the movements of patients with disorders like Parkinson’s disease and multiple sclerosis.

This is just the latest in a series of projects using radio signals to mimic X-ray vision. CSAIL has been working on similar technology using Wi-Fi signals for several years, creating algorithms to recognize human forms and see motion through obstructions. In the future, they hope to expand the system to be able to recognize movement with 3D images rather than the current 2D stick figures.