Privacy advocates got access to Locate X, a phone tracking tool which multiple U.S. agencies have bought access to, and showed me and other journalists exactly what it was capable of. Tracking a phone from one state to another to an abortion clinic. Multiple places of worship. A school. Following a likely juror to a residence. And all of this tracking is possible without a warrant, and instead just a few clicks of a mouse.
It also won’t work since the service has enough precision to know whether you go in, and for how long. The real issue is that mobile phones are continuously broadcasting their location to any device that wants to listen, even if you turn wifi and bluetooth off.