Back to the subject of bikes, what about a CVT drivetrain? The rider would have some sort of control to dial in his or her preferred cadence. and the bike would vary the gearing to always keep it there. It would be like a fixie/SS but you'd have an infinite range of gears. Have everything done in the rear hub, and a single chainring. If you're going to make gear shifting automatic, I'd prefer something like that.