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.
The first time I heard about this was in 2013 and, in 2019, I had a local government management class where wifi sensing in busy downtown areas and stadiums was discussed as a plus side to municipal wifi installations. In the latter case it was described as being available not too far in the future.