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.
Yeah it’s nuts. There’s also https://www.tommysense.com/ which is planning individual presence detection and location tracking within rooms using an esp32 mesh, but that’s closed source