Yeah, technologically, it's not only possible but even simple. It would come down to the washer knowing how much water it needs for a cycle and the softener knowing how much soft water it can provide, a means of getting that information from each of them, and then an if statement with a > check and a way to tell the softener to cycle and washer to start.

I wonder when an appliance hacking community is going to rise up. I know that all that information is available to my water softener controller because I use it to manually check that before running the laundry or dishwasher. So a custom controller could add network capabilities. Then just give it an API so it can be queried and directed and the actual smart software can exist entirely on the server.

Kinda makes me want to buy an extra softener to hack and see if it's as easy as I suspect it might be, but don't want to try it with my only one because I also suspect I'm wrong lol.