They can triangulate the location of wireless devices without line of sight, by repeatedly measuring 1-dimensional distance data and sampling from multiple measuring locations. Kinda like how GPS works. The data is positioning only, and indirectly/approximately derived.

I wouldn't call that "seeing through walls" as if it's an x-ray camera. I might say "it can see the 3d position of wireless devices through walls, but no visuals, it can just see the spots the things are at."

They can also reverse-engineer what the device is likely to be, by cross-referencing its unique MAC address with the manufacturer that has reserved those addresses. So, something by Apple is probably a computing device or an AirPort router or whatever.

I dunno, man, this headline feels way too hyped up. A persistent person could definitely profile where stuff is in your building, but that's a hell of a lot of effort to case a joint than just traditional means, IMO. Sounds like the kind of stuff only spies would care about, or organized crime maybe.