The trick is known to just about every small-time crook in the cellular age: If you don't want police to know where you are, take the battery out of your cell phone when you're not using it. Had that trick been taught at the CIA's rural Virginia training school for covert operatives, the Bush administration might have avoided much of the crisis in Europe over the practice the CIA calls "rendition."

http://www.truthout.org/docs_2005/122705M.shtml