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.

In telecommunications construction we are taught to make ample use of the "hammer test" when working on and around poles. The difference in sound between a good pole, a marginal pole and a completely rotten pole is quite significant.

You could of course just bury your lines.