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.
I’m not sure what you think an “example” would look like. It’s not taking a photo of you, it’s measuring what’s distinctive about the way you personally mess up radio signals and how it differs from how other people mess them up. Internally it’s just a ton of numbers.