BTW, about 15/20 years ago, Shimano made the "Auto-D 4 speed" system. Same concept, but required batteries instead of using the dyno front hub. Similar servo mounted near the bb to pull the shift cable that ran to the rear internally geared hub. But the slick feature of the Auto-D was the mode switch that allowed for conservative or aggressive shift points and a third mode for manual shift with soft touch shift buttons. That 3rd mode was the best. You shift when you want, not some transistors that just can't predict your riding. The soft touch worked very well. Shimano sent a bunch of kits to various bike manufactures to see how they would incorporate them into bikes, then Shimano hauled those demo bikes around to a bunch of bike dealer shows to try to generate interest among dealers. I got to ride some and they were really nice. The Lime has a dumbed down version, no mode selection, just fully automatic and a very conservative gearing. The only improvement the system on the Lime was the use of a generator front hub to power the servo (no batteries needed) and to provide the info for the shift points. ie, the faster you go, the higher the voltage the hub puts out so that voltage could be used to trigger the servo. I recall the Auto-D used a traditional magnet in the spokes & sensor to measure wheel speed and shift accordingly.
rick