Not pron, but the Japanese have it down pat when it comes to bicycles.
I was once in Kyoto, huffing up a 20-30% grade of an underpass tunnel, when a 70yo man, with his freakin' wife sitting on the back, came up from behind and passed me like I was standing still!
Later, I was told he probably had an electric-assist wheel.
-The only one that seems to be available here is the E-bike wheel at $600.
-The Green Wheel was promised to be a few hundred but isn't for sale(yet).
- There are others for sale with bluetooth/data tracking/unecessary crap that is also available.