You plug this into your bicycle dynamo and out comes electricity to charge your shit with if you're going at least 12kph ~7,5mph.
Very cool for people who do multi day bike tours and having tested one personally: Yeah, rules!
You might have to do some finnicking with a powerbank that doesn't require you to replug it after it stops charging - I mean you're gonna go below 12kph eventually - but hey, you get some volts out of it to keep your phone or whatever other tech going if you're on a multi day ride with sparse outlets
Here's some data if you're into that sort of thing
500mA isn't a lot but I guess people usually cruise at >12kph and it doesn't take much to keep a phone alive all day, it's not like it's probably getting heavy usage while touring (unless you're one of those people that twitch streams it lol)
my eternal average touring is at like 18kph and I'm by no means a fast boy