Thieves are using mobile phones to detect laptop computers and other equipment hidden in cars, police have warned.
West Mercia Police believe thieves are using Bluetooth-equipped mobile phones to detect hidden electrical equipment.
Laptops and satellite navigation systems, hidden under car seats or in boots, have been stolen during a spate of car crime in south-west Redditch.
Sergeant Julian Smith called on people to be more aware of the dangers.
"What is most likely is that if somebody leaves a laptop in their vehicle, even if it's hidden away, if it's on stand-by somebody with Bluetooth on their mobile phone is able to detect the presence of that laptop," he said.