[slowburning]

You can fix your GPS coordinates on certain phones. See this presentation for more information https://www.youtube.com/watch?v=F1VttfQFTWE

He talks about being able to fix your GPS coordinates to static values. Also being able to fix your list of cell phone towers so you never end up on someone's femtocell. There's also a really cool cell proxy setup for fully anonymous calling via a proxy cellphone

[reaperducer]

Good information, but useless for what we're talking about here.

The location data that the cell phone companies are selling is gathered by the cell towers for the fundamental operation of the system. It doesn't come from GPS.

Rule of thumb: If you're emitting a signal (wifi, cell, bluetooth, smoke, etc...) you can be tracked. How accurately only depends on the number of receivers.