Versions of 'Eco Mode" have been around for decades, both mechanical and electrical. Mitsubishi had a "Super Shift" manual trans they marketed in Japan late-70s and early-80s here in the US (Twin-Stick) which had a separate shifter as a high-low control. This second, smaller stick was marked 'Economy' for the higher gearset, and 'Power' for the lower gearset, making this an eight speed trans.

And of course GM tried to do great things with the 8-6-4 engine.

As for the newer 'Eco' modes, they are great for long cruises, but are dangerous for daily driving. If you're in 'Eco' in, say, a KIA, at an intersection and want to scoot out ahead of another car, you can stuff it to the floor and the car will barely move, with no real acceleration. For most cars, the 'Eco' mode is non-adaptive, so it won't 'learn' as you drive it as it would probably defeat it's intended purpose.