Can you trick the Google Home by turning the coffee maker on yourself? i.e. is it just remembering the last state it set, or is it able to query a device for current state?
I don't have a coffee maker, but I just tried this with my Philips Hue lights and it was able to get the right state even after I turned the lights off manually through the Hue app.
3) is true with all hue lights, so that you can easily override using the good old physical switches.
However, are you sure about 4?
I had power outages sometimes, when the power comes back, all the hue lights gets on (Not cool when it's 4 am by the way), but then I'd just press "Off" on my hue light app and they'd all turn off.
If I remember the Hue API, you can send a new state to the lights not matter what the previous state was, so I'm not surprised this works correctly, which is why I'm confused about your step 4).
Are you trying to turn them off via a Echo command specifically?
I'm using my own CLI script to control Hue lights[0] and I confirm that you can set the state of your lights directly, without referring to or even knowing the previous one. The API is pretty straightforward.
I suspect that even the vanilla Hue app on Android does that - given the way I often manage to switch the lights before the app UI figures out what's their current state.
4) is not true, I just tested it. If I leave the app open it does take a few seconds to sync. If I close the app and reopen it, it displays the correct status. This is using the official Phillips app. Some other apps may not read the status, but they clearly could.
