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.
Run a headless browser that does random searches at random times across different social media and search engines and have it click random ads.
you can essentially already do this with TrackMeNot and AdNauseam
This was part of the fictional operating system in the book Little Brother. I think it inspired similar features in a particular real life Linux build too