Scientists in Germany have demonstrated a startling new form of surveillance: identifying people using nothing more than ordinary WiFi signals. By analyzing how radio waves bounce around a room, researchers can effectively “see” and recognize individuals — even if they are not carrying a device and even if their phone is turned off.
that’s a trivial problem to solve. combine this with a camera for facial recognition in a public space. then you’ve got wifi signature combined with the photo/video for facial recognition. then presumably you can use the WiFi signature anywhere else, even without the camera and be able to identify people.