The idea was: a normal light switch, you can turn it on or off with your finger, and it will stay that way, even if power goes off. A remotely controllable switch, the easiest version would be a relay, that stays on as long as it is powered, and goes off otherwise. I wanted something that would be remotely controllable, but would stay in the last position no matter whether power happened to go off or not, and wouldn’t use power to stay on. There were bistable relays like that, with two coils and permanent magnets: energize one coil, it switches that way; energize the other, it switches that other way; with no power, it stays in the last position, just like if you had flipped it with a finger. Only… those bistable relays were bulky, expensive, and you couldn’t flip them with a finger. I wanted both things: flip with a finger and stay, and flip with a signal and stay.

Nowadays there are some switches that have a sort of bistable relay built in, a couple coils that switch it on or off depending on which one gets energized, and it stays that way… but in the meantime the whole idea kind of became obsolete. Now you get SSRs that use negligible amounts of power for a very long life time (no moving parts), and dirt cheap microcontrollers with also negligible power draw, that come with enough memory to store the last switch position along a firmware to connect wirelesly.

The “purist” in me would still want a bistable electro-mechanical switch, but the practical side tells me “who cares”.

Now my pet peeve is that those smart switches, don’t all come with all sorts of sensors, which are also dirt cheap nowadays.