There's a reason why Germany/Austria/Switzerland don't usually have state-indicating toggle switches and it's because toggle switches make no sense in multiway switching [0] systems where multiple switches control the same lightsource.
I'm not sure how common multiway switching is in the US, but it's certainly super common in Europe and I guess that's why we use non-state-indicating switches, even in circuits with a single switch, because so many circuits are controlled from multiple switches that there's no point in having them indicate state.
Is there really not a good and robust solution to this? Like, say, a condensator that charges for up to 20 toggles and a tiny motor that actuates all the switches that aren't depressed manually? I'd have this over digital switches any day.
Motor inside screams "not robust", "quick to break" and "much more expensive to manufacture" to me. That's probably the reason I haven't seen anyone making such switches. Damn how much I'd like them though.
The method I have seen for some 3 way switches is for the switch to glow when off. This is used for finding the switch in the dark but happens to show state as well.
I think putting a light only is not enough. LEDs at night at home, no matter how weak, are an annoyance. I'd also put in a motion sensor that detects movement around 1.5m from the switch and lighths up the LEDs gracefully. A light sensor to set the strength would also be good. Fallback if any of the sensors are broken: keep them lit on the lowest setting.
IMO you can make things smart, but connectivity is only the answer once you figured out all the other stuff. Otherwise it's like getting the internet on an 8bit Atari.
We have this in the US, but we do it with toggles. Turning the circuit on with one switch and off with another leads to the curious situation of both switches being on but the circuit being dead. It's immediately obvious that this is the case, though.
Isn't that the intended behaviour? Also, on-off state indicating switches don't make much sense in such a circuit. What works is having a small (typically orange-ish) light inside the switches that indicate the state.
Anecdote: We have those in my apartment but they're wired up to be on when the circuit is off. This is implemented in what is likely the worst possible way. We haven't quite figured them out but when off, there's still juice on the line - enough to make some cheap LED bulbs flicker, but not enough to light up a "classic" light bulb or an LED with high resistance. It's great for making electricians cry about the stupidity, as I can take out one of the LEDs in the hallway (when it's off) and the others start to do a strobe effect.
I'm not sure how common multiway switching is in the US, but it's certainly super common in Europe and I guess that's why we use non-state-indicating switches, even in circuits with a single switch, because so many circuits are controlled from multiple switches that there's no point in having them indicate state.
[0] https://en.wikipedia.org/wiki/Multiway_switching