Doesn't this still fall foul of existing surveillance protections, though? The police can't circumvent legislation by just paying a PI to stalk you instead. Doesn't this fall into the bucket of turning the seller into an agent of the state?
This could be fixed very simply by a law. The chances of such a law being passed are sadly extremely low.
Actually, they are starting to crack down on some of that with the recent SCOTUS case on cell location tracking. I forget the case name, but that was within the last 4 or so years.
Why would they need to? Stalking you doesn't require a warrant. Breaking into your house, for example, would require a warrant, but a PI can't do that any more legally than the police can.
If your neighbor's Ring camera is pointed at your front door or living room, the police can legally acquire the footage without a warrant.