WiFi routers can see people through walls. Here’s how it works

I read about this a while ago when I was trying to see if I could build a device to see/hear through walls. It's possible just hidden behind a lot of beauracicy/acadamia bs.

Some consumer wifi company - linksys eero possibly? - some years ago was rolling out a home security feature which used signal differences in the mesh links to detect movement in the house. Not quite 1:1 with mapping, but similar.

There's been a bunch of "wifi as passive radar" in academic stuff for 10+ years, but w/out the modern image recognition stuff to boost it; most of if lacked public attention due to either academic paywalls or the difficulty of obtaining SDR gear in any affordable way at the time.

There are old household alarm systems based on this tech from the 70's. I think there were two components - VHF transmitters, and a receiver -- and if the receiver detected an change in the receiving pattern, it was because something moved between a transmitter and the receiver, and it would trigger.

Fuck I'm old.