Originally Posted by Milton Keynes

Too late. Back when I bought my first mountain bike in 1990, I think it was, there was an optional "automatic shifter" that attached to the back of the bike and the rear derailleur somehow, and automatically shifted into a lower gear when it got harder to pedal, and into a higher gear when you spun the front crank too fast. I thought it was superfluous, and I think I was right since it's not hard to manually shift gears on a bike. It likely would have added a bunch of unneeded weight.