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.
You don’t need to build your own router. All you need to do is flash open source firmware like OpenWRT on a supported router to prevent it from spying on you.