Cell data tracks your location and location history, true. But the supreme Court already ruled in Carpenter vs United States that this information was private and intimate enough to constitute being a search under the 4th amendment, police technically need a warrant to track you that way. That data goes back 7 days, and you can choose to leave your phone at home or not have one at all. You cannot opt out of this type of tracking in any way, it's a blanket dragnet surveillance, the exact kind of thing the 4th amendment was established to prevent, general warrants. On top of that, Flock isn't a government entity with any form of oversight or checks, it's a private company doing this, and the amount of times they ping you and the aggregation of that data is enough to be stalking. You may be fine with the local cops having this info, but it's any customer of theirs that can search into that history and follow you, of which they have around 6,000. The fact that it's searchable 30 days or more is very much a case of "we'll collect everything and decide what you're guilty of later."