Does a bike exist such that you can program it with what load you desire and it will shift gears for you based on that load or maybe never exceed that load? For example, suppose an older person has some knee trouble but doesn't like to shift gears and doesn't want a 1 speed bike so they desire a bike that can be programmed with a maximum load level so that if either the terrain or headwind or hill or any combination would put the bike at a greater load, the bike would automatically sense this and adjust the gear ratio accordingly. For example, someone is on flat paved ground at a comfortable output (perhaps 100 watt equivalent). It would be slick if when that person encounters a slight upgrade that the bike would sense a reduction in speed and calculate the loss of power due to less cadence and adjust so the load feels the same to the rider.
I am also wondering if this algorithm would differ much from constant cadence or if they would be identical or virtually identical. I think it would be significantly different since suppose someone programs in constant cadence of 60 RPMs. With maximum load instead dialed in, if the terrain makes it easy to pedal (and for example there is a tailwind), the rider might be able to use a high gear and pedal slower than 60 RPMs but still maintain desired roadspeed (10 MPH for example). This has happened to me in real life scenario. I think constant cadence would be somewhat annoying since sometimes the circumstances dictate much less load so why pedal at 60 RPMs when in that situation you can get by with 30 or so? It would be nice if the bike would also sense cadence and determine if you "underpedal", it is cuz you are wanting to slow down or cuz the load is light (tailwind for example) so a taller gear can be chosen. Not an easy algorithm to get right in all cases.