Anyone who has ever been intrigued by ads for x-ray specs in the back of a comic book will appreciate the latest work out of MIT, which advances technology to “see” through walls.

Using WiFi, a team at Computer Science and Artificial Intelligence Laboratory (CSAIL) is now able to “see” a person on the other side of a wall and precisely track their movements, even if it’s something as subtle as giving a high five, according to new research to be presented at the Conference on Computer Vision and Pattern Recognition next week.

“People have been trying to detect people through walls since the 70s,” said Dina Katabi, a professor at CSAIL and the lead researcher on the project. “Around 2013, we showed that we can track people accurately. What’s new here is that, for the first time, we can create a dynamic skeleton of the person, their posture, and how they’re moving.”

Katabi told me that previous versions of the technology developed by her team were able to give you the position of the person and kind of their vague, blob-like outline, but not precise movements. Now, they say they’ve been able to train a neural network to interpret the way radio WiFi signals bounce off a person’s body and translate it into the movement of 14 different key points on the body, including the head, elbows, and knees.

A data set to train the AI didn’t already exist, so the team had to make one by manually creating stick figures of human movements based on images they captured through both the wireless device and a camera. By showing the figures to the neural network along with the WiFi signals, the network was able to learn which radio signals were made by each movement.

“Let’s say the police want to use such a device to see behind a wall,” Katabi explained. “It’s very important to know if somebody is standing in a position that indicates they are holding a weapon, for example. All of that you can’t do with just a blob.”

Along with law enforcement applications, Katabi said the technology could be used for interactive gaming. But the team’s main focus is on healthcare applications, particularly for neurodegenerative diseases like Parkinson’s, Alzheimer’s, and Multiple Sclerosis. They’ve been working with experts in the treatment of each of those diseases, where being able to monitor a patient’s daily movements and gait with precision would provide doctors a wealth of information they can’t get from a half hour check up.

Of course, once you start introducing something that would make it really easy for the government to spy on us through walls, people naturally start to worry that the government might use it to spy on us through walls. Katabi said privacy is something they’re deeply aware of when developing new technology like this.

“Particularly in the current climate, this is an important question,” Katabi said. “We have developed mechanisms to block the use of the technology, and it anonymizes and encrypts the data. And then there is a role of policy that protects the user and doesn’t stifle innovation.”

Privacy is always going to be a concern with new technology, especially something that can see through walls, but it also comes with many possible benefits.