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.

In outdoor rock climbing smacking rocks is an integral part of ensuring the rock you're trusting your life with is in fact worth trusting your life with.

Only if you go outside well-secured sport climbs where you don't have to think about that (but still its a good idea to check the state of bolts for any visible damage due to rot and rust). And even then, some rocks are hollow and still can sustain next 5000 years of literally any climbing on them, some are more solid and will come off if somebody over 80kg hangs on them. So its more about calming one's mind rather than objective good quality test.

Most folks in Europe climb only sport routes, or then do some variant of proper alpinism once on wild unsecured terrain.