Android has had Trusted Voice for a long time where you train it against your voice by saying "OK Google" three times. The goal is to prevent unauthorized users from accessing your information while the device is locked. It's far from secure (Google says as much while you set it up). In my own experience my wife can trigger mine occasionally as well as just random noise from the radio or videos. I do get fewer false activations though so I guess it's better than nothing.

Maybe this new neural network backed detection for Home will improve upon Trusted Voice.

It's so secure it seems I can only talk to it in a small quiet environment at similar distance. In my car I get no reaction.

Maybe it's hardware related? My Pixel hears me in the car with music on.

I can't say. I've never used it extensively, but I'm tempted to say that it responded a bit better before I used the secure voice. I even rerecorded my voice, no effect. alas

It doesn't mean it can precisely fingerprint you. Only that it can fingerprint you enough to tell you apart from 5 other people.

It interesting, the person I'd say I sound most like in the world is my Dad. Humans often fail to tell us apart on the phone. I assume this is true for a lot of families!

I just hope any family member can turn off an alarm I have set. I could be out of the room or on the phone and they should be able to turn it off.

It will be decently trained on the wake word itself and probably not on anything else you say.

if you could change those words ("ok google", "hey google") to some passphrase it could help in many cases