A slew of GPS devices designed to spy on people have become popular in recent months. Take for example the PTX5 Live GPS Tracker. It’s about the size of a deck of cards, and can be attached to the undercarriage of a car, or hidden inside a glove box or backpack to track an individual. Once switched on, the device can be tracked using a Web application which shows the device’s location on a map. GPS trackers have become an essential tool for private investigators. Some parents are using them to keep tabs on their teens, jealous partners are using them to keep track of their mates, and criminals are using them to track victims. Last week the Supreme Court found that while these devices may be gaining in popularity, they are not okay for use by law enforcement officers – at least not without a warrant. The courts findings overturns a case where a nightclub owner was sentenced to life in prison for drug trafficking, since the conviction was based on GPS evidence linking him to the location where the drugs and money were stored.