I have electronically actuated (as opposed to cable actuated) gear shifting on my bike. It's becoming way more common these days, though...but still, it's a pretty expensive piece of kit for quite marginal gains.
Front and rear derailleurs are servo controlled. These connect to a central unit that also has the shifters connected to it. This central unit can communicate with a bike computer (via ant+) to show gearing.
In addition, you can set it up so that when you shift the front derailleur, it automatically moves the rear derailler. You might want to do this in order to keep roughly the same gear ratio when changing chainrings. Or, there is a mode where you just shift up and down, and the system manages the shift for you, shifting either (or both) derailleurs, simulating a 1x drivetrain.
All of the popular group sets have a version of this: shimano, sram, and campagnolo.
It’s rechargeable battery powered. The front derailleur takes more power to do its thing, so when power is low, the system automatically drops you into the small chainring and disables the front shifting. The idea is that this will get you home relatively comfortably since you still have the full range of your cassette.
Still…a full charge lasts me many weeks of riding, and I ride quite a lot…about 10-15 hours a week.
Also, I’m describing shimano’s version of electronic shifting, where everything is connected physically via electric cables, so there’s one battery (mine is hidden in the seatpost). Sram’s offering has every component (derailleurs, shifters) communicating wirelessly and every piece has its own battery.
Nothing wrong with that. There’s something to be said for going with simplicity. Way easier to fix if something goes wrong. If I was doing some really hardcore touring through remote areas, I would definitely favor friction shifters for this reason.
WTF, first I'm hearing of this. Sounds really expensive. Is this a road bike thing? Sounds like a road bike thing, I can't imagine the mountain bikers wanting something like that.
It's becoming pretty standard on the 'mid tier' specced mountain bikes. Anything with sram axs in the name. With that said the mid tier for mountain bikes jumped from 3-4k to 5-6k usd over the past few years.
Oh wow, when I was still biking actively, dropper seat posts were only becoming mainstream; shows you how long I've not ridden. And now there are electronic ones!