Flock can alert when any specific car drives by. No warrant is required to use this feature.

So, I won't follow you, but when you _do_ leave, I'm going to call some people to let them know that happened. Still cool?

Eat your heart out. It's also a completely legitimate law enforcement technique.

Having this surveillance done by human beings rate limits the process to, in theory, focus it on actual criminals. Requiring warrants for the more invasive and persistent techniques adds another layer of accountability.

You're bootstrapping your argument with an assumption that there's something to account for. Public activities are public. You're shifting the accountability from the actor to the observer.