While it's not quite x-ray vision (at least, not yet), this sensor is capable of detecting people through solid walls. It's being developed and tested in cooperation with the U.S. Army, in the hopes that technology like this will make it possible for soldiers to get some clues about what's inside a room before they have to go in.
Called the AN/PPS-26 STTW (which sort of stands for "Sense Through The Wall"), this device is essentially a miniature radar system, complete with a transmitter, receiver and display wrapped up in a five-pound beige package. To use it, you just stick it up against a wall or door, and it'll project little yellow dots on its display, giving the approximate bearing and distance to what it senses in the next room over.
While it sounds pretty fantastic in principle, the system does have some significant limitations. For starters, it doesn't detect people specifically — it just detects motion, and it doesn't discriminate by size or composition. So, those little yellow dots could be men, women, kids, cats, ceiling fans, bears, robots, unicorns or just about anything else that moves. If something isn't moving, the device won't detect it at all, meaning that a person holding their breath will turn effectively invisible. Also rendering things effectively invisible: metal surfaces and walls over eight inches thick, whatever they're made of; both will prevent the radar from penetrating.
Still, the hope is that soldiers will be able to use the STTW to give them some idea of what might be behind a closed door, which is infinitely better than no idea. And it's easy to imagine how this technology may evolve in the near future, by providing more specific details about the size and composition of what it senses. Getting walls to become functionally transparent is something that DARPA has been working on for a while now, and a step in this direction for them means a step toward x-ray specs for all of us. For, you know, safety. And stuff.
Via Danger Room