This.
I read the opinion and it basically tells us what we already knew. In places where the public has access, it's all fair game. In the privacy of one's home, they can record what is specifically related to the reason they are there and only what is not deemed to be "private". What I take this to mean is, if the officer(s) are questioning you just inside the door of your home and your wife/husband is on the phone talking with somebody else, anything going on in that phone conversation is considered "private". I won't get into other examples, but that's a good enough one. Or maybe, you are talking with officers and you have to take a phone call. The phone call is not related to the reason the officers are there so the contents of the phone call are off limits.
If Rapgood would give his opinion about my line of thinking, that would be great.