I see that restful switch can poll for the current state, but is there some way to allow the remote to push state instantly to home-assistant?
Similar to how wemo does it, by accepting local packets on port 8989 (I think). Or is there some way to create a very limited token and just use the websocket API?
To close the loop on this, I ended up using MQTT which works perfectly. I can add an MQTT sensor in HA, and the remote device can publish values for instant updates. (And I can even add control channels without much effort, should I need them in the future)