Helium comes the closest to being "actually potentially useful" of all the cryptocurrency gobbledygook. But, amusingly re: your point that it could be done in

Helium comes the closest to being "actually potentially useful" of all the cryptocurrency gobbledygook. But, amusingly re: your point that it could be done in a centralized way: recently my wife's (sigh) Helium miner stopped working for a few days because... centralized stuff failed! So as far as I can tell, it's a bit of huckster speculation on top of a centralized protocol. Which, theoretically, might one day compensate random people for putting up 20 watt transmitters to spread ultra-low-bandwidth internet access around (right now we get compensated in VC-funded scrip aimed at expanding the network). Not terrible, but the crypto bits do seem only lightly glued on top of the basic business proposition.