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.
Fascinating project! Definitely sounds like at best it might detect that somebody probably fell down, but not that Old Man Jenkins is having a bowl of Lucky Charms instead of Raisin Bran and his blood pressure is a little high - which seems to be the conclusion people are jumping to here.
It definitely depends on the circumstances. With 60 GHz radar e.g. you get quite a good distance resolution and can detect e.g. breathing rate really well (from the torso movement during breathing) and things like how many people are in a room, etc. But its always very dependent on the environment, your settings, subjects, noise, whatever. That’s why I said its typically not practical. By using dedicated devices perhaps, and most of these kinds of news are about people who use dedicated devices, but that’s like putting a camera in your home. When you have to abuse an existing communication channel, probably not so realistic.