Not at this stage. A malicious firmware in future perhaps, but the hacker would still need 3 devices (I read the article :D) in the room, all with compromised formware.

If this application proves to be useful, then they will likely continue building on it to allow partial imaging with two or even one device, as well as mapping of other objects besides people, and through walls and other objects which are permeable from a WiFi POV.

But what they've done on this pass is fundamentally a form of reverse triangulation; using the data from each of three waypoints to discover data points within their boundaries that can't be seen.

Think of it like 3 people standing each on the top of a hill, looking at an object in front of them. They all relay information to a 4th person about what they can and can't see. The 4th person can then use this information (after a lo-haw-haw-hawt of calculations and line drawing) to draw a reasonably accurate 3D rendering of the object.

Actually, from a WiFi perspective it's like there's a big object made of clear fluid between them, so they're telling the fourth person not only what they can see, but hoew clearly they can see it. Hence the need for insane numbers of calculations that probably weren't even reasonably possible a decade ago.