The Secret Service has used a technology called Locate X which uses location data harvested from ordinary apps installed on phones. Because users agreed to an opaque terms of service page, the Secret Service believes it doesn't need a warrant.
Agreeing to location services for the purpose of performing the apps intended use, is not the same as agreeing that the government can track your location on a whim. Where the fuck are the constitutional lawyers who fight this kind of egregious constitutional violation?
It shouldn't be though. Nothing a company gleans from your use of a product should be available for purchase by any third party. This should have been legislated two decades ago.