It sounds like something Q might have added to James Bond's Aston Martin, or perhaps a gizmo from Lady Penelope's Rolls-Royce in Thunderbirds. But the GPS tracker bullet that police can fire at the touch of a button is real technology, being used by police forces in four US states.
Made by a Virginia company called StarChase, the system uses a compressed air cylinder mounted behind the radiator grille of a standard squad car to fire a projectile containing a GPS tracker.
The aim is to cut the number of dangerous and expensive high-speed car chases by enabling police to tag the car in front, then track them at their leisure. It is activated by a control panel mounted on the dashboard, meaning the cops can use it while moving. Once they have hit the car in front, the chase car can fall back.
The projectile, or tag, can stick to the car in front and transmit a signal back to the following police car and the police station. It measures 11.5cm by 5cm, and has a soft foam tip that uses a non-caustic adhesive to stick firmly to car bodywork, rather than magnets, as many modern cars use plastic and fibreglass in their construction.
Each launcher can hold two tags, and uses a laser sight to aim at vehicles ahead. As well as being controlled from the car, it can also be fired by a remote key fob.
Each StarChase system costs $5,000 to install, and each tag costs $500. While that might sound expensive, high speed chases currently cost millions of dollars a year in damages - not to mention the human cost. In the US, the National Highway Traffic Safety Administration says that police chases are estimated to claim the lives of 360 people - officers and civilians - every year. Lobby group Pursuit Safety claims the real figure is "two to three times higher".
Senior Lecturer as Leeds University Dave Allen recently co-authored a report into the future of technology for the UK police. Speaking to the BBC, he said that "This sounds like interesting technology and there is a clear operational use for it. I think the costs will fall rapidly and we will see them being used routinely in the not so distant future".
Allen also pointed out that there are potential privacy issues at stake, that would need to be addressed before the technology was implemented on British streets.
"There are other ways to track vehicles and this could raise some civil liberties issues," he said.