Yep. There was a Kervelo concept chainless recumbent design that worked similarly and looked very cool (with a 14-speed hub!), but I hear they couldn't get it funded to actually be produced.

> "there is only one multi-geared commercially available unicycle hub, and it only has 2 gears, and costs $1500 (Schlumpf drive)"

The Kwiggle folding bike in Germany[1] took over manufacturing of the Schlumpf drive in 2023[2] and uses it for their 6-speed option. It's in the bottom bracket and shifts by hitting the axle left/right with the heels. (costs ~€2000 and surely the front gear is not three quarters of that?).

[1] https://www.kwigglebike.com/en_US/

[2] https://www.drive-mobility.com/en "We, KwiggleBike GmbH, have been managing the business of Haberstock Mobility GmbH since 01.04.2024. We have been manufacturing all Schlumpfdrives since mid-2023"

There are 2 schlumpf drives; there is a bottom bracket-compatible one like you describe. That is used for recumbent bikes and a few niche things like Kiwgglebikes. However, they still power the wheel with a chain. The unicycle hubs, which are the same as shown in the cyclauto, have no chain; the hub is also the center of all the spokes on the wheel. But yes, they are basically the same thing.

I'm sure it doesn't cost $1500 to produce, that's just the cost to consumers. My point wasn't that it's ridiculously expensive (which it is), but that this seems like a really high hurdle to produce the cyclauto; no other company is currently producing the unicycle version, and even if they can manufacture them for, say $500, that's still astronomical compared to if they used the cruzbike model.