As GPS tags and monitoring equipment reach rock-bottom pricing for law enforcement around the country, they're being used to track potential criminals' 24/7 whereabouts far more frequently. Currently, such usage does not require a warrant, but the Washington Post is reporting that growing unrest in the courts and amongst privacy advocates may change that.
Nobody's arguing that it's not easier and more efficient to track a criminal with a GPS tag than by trailing him with a man in a car, Herc and Carv style (even though they like GPS tags, too). What is being questioned, though, is whether this practice can be put into place to track anyone, without having prior consent for a warrant. Currently the answer is an unofficial (ie: a largely unchallenged) yes, as long as the vehicle is tagged on public property and not, say, in the garage. What privacy advocates are arguing, however, is that GPS tracking without a warrant is now approaching invasive, 24-hour surveillance state levels as the gear gets cheaper and more widespread by the day.
A recent ruling by the Washington State Supreme Court is among the first to swing the balance toward requiring warrants for tracking. But until a more definitive ruling, you'll have to stick with dubious GPS bug detectors if you're paranoid. [Washington Post via Slashdot]