No, Turning On Your Phone Is Not Consenting to Being Tracked by Police

https://theintercept.com/2016/03/04/no-turning-on-your-phone-is-not-consenting-to-being-tracked-by-police/

The Maryland Court of Special Appeals on Wednesday upheld a historic decision by a state trial court that the warrantless use of cell-site simulators, or Stingrays, violates the Fourth Amendment.
The trial court had suppressed evidence obtained by the warrantless use of a Stingray — the first time any court in the nation had done so.
Last April, a Baltimore police detective testified that the department has used Stingrays 4,300 times since 2007, usually without notifying judges or defendants.