That's the point though, if your Nest device starts automatically recording your guests and you don't warn them, could you be liable in a 2-party consent state?

But on the flip side, Google Assistant devices don't start recording unless it gets the "OK Google" keyword, so it's not like it's randomly recording everything. You specifically have to turn it on (albeit it can be turned on accidentally if it misdetects an OK Google). Is this somehow different from Nest devices?

its listening for that keyword, whose to say its not listening for others

As an EE, this is the exact point of failure I see even from tech people on this topic.

There is LITERALLY ZERO way to tell that your “Assistant” is not listening for words like Trump or Sanders then marking down in a log if they were mentioned with other words like “Fucking” or “Communist” or whatever.

No one has or realistically can do a full reverse engineer of the firmware here, you’re talking about the same protections used in game consoles and smart phones.

The “research” into “is my Alexa spying on me” looks at large pattern encrypted traffic and determines they aren’t always uploading. But they absolutely could be collecting metadata of what you talk about without the words themselves.

The meta data of your habits and conversations for a month would be kilobytes at most and sent in a single HTTP/MQTT message that could look a ping or keepalive or some normal traffic.

Where I live this is illegal. Unless you mean when both parties actively consent to it, which in this case is not happening.

California is a pretty relevant example.