Probably a whole conversation on how to track appliance state (on/off). Depending on the specific type of appliance, I think people tend to use smart plugs/receptacles that track power, vibration sensors (esp. for washers, dryers, or dishwashers), or even time-based variables.
I use IotaWatt, which is an open WiFi-based power monitoring solution using this awesome driver written by @ogiewon.
If the device in question isn’t on a dedicated circuit, then I’ll just use a smart-plug typically.
Regardless of the specifics, I think a “power meter”, “switch” or “vibration” capability would address most the use-cases to start.
