It seems the US Court of Appeals for the Ninth Circuit has ruled that it is acceptable for police to install a GPS tracking device in your vehicle without a warrant.  I am pretty certain this case will go the Supreme Court eventually, at least I hope so. 

If you read the original story, they have a link to an article at the bottom of how you can scramble the GPS signal. Gizmodo is getting more and more political.

Original Story: Our Worst Nightmares About the Government Tracking Us Just Came True [Gizmodo]