I'm curious what the charges would be (loitering, stalking, harassment?).
It's interesting as a comparison to Flock. Their arguments (and those of their law enforcement clients) have often relied on the notion that they're simply automating activity that has always been legal, and that people don't have a reasonable expectation of privacy when in public view.
But I'm not sure that's strictly true anymore (if it ever was). I think you're right that private citizens performing these actions would very quickly attract law enforcement attention and quite probably arrest and civil/criminal charges.