WiFi signals can measure heart rate

Hey, I heard about how utility pole inspecting helicopters are able to tell the good/rotten state of wooden telephone poles by the reverb pattern of sound waves coming off the poles from the rotors -- it seems to me the whole field of non-invasive sensing (and using existing/ambient emission sources) is getting pretty impressive.

What kind of helicopter of what size are we talking about here that can actually get close to a utility pole with wires going across?

Look up "Helicopter tree trimming" and prepare to be amazed.