Do laptop detectors really exist?

Many people complacently leave their laptop computers in their cars, and quite a few of them have had their laptops stolen.

Often, it happens even when they hide the laptop under their car seats or in their car boot.

How can the thieves possibly know which car to strike?

According to this report, it's because they have a special device.

Does such a device actually exist? The police believe there is, although they have not been able to get their hands on one.