How thieves know there's a laptop hidden in your car

You conceal your laptop in the car from prying eyes and return to find it gone. Still wondering how the thieves knew? The mystery as to how thieves could single out vehicles for the laptops stored inside has been resolved with the arrest of two Indonesian men. The key to the mystery is this harmless-looking gadget called an inductive amplifier.
This came to light after Selangor police arrested the two foreigners in an ambush at Kampung Changkat, Gombak. Police recovered the gadget and seized several laptops, custom-made break-in tools, handbags and watches among other items. The suspects are believed to be behind at least 20 cases of theft from cars.
An inductive amplifier, an electronic device similar to a handheld metal detector and as small as a hairbrush, is used to "sniff" out laptops kept in parked cars. The conventional use of the inductive amplifier is the location of breaks in hidden wires, even buried in concrete. The typical wire detection range in a concrete wall is 10-20 cm.

A check on eBay revealed that the inductive amplifier is priced about $60. This means anyone can easily purchase one and start a laptop stealing business.
After knowing about this, I would strongly reconsider putting my laptop in the car boot unattended ever again. My previous practice was to remove the battery from the laptop first before keeping the laptop in the boot. I thought that the laptop detector works by sensing live circuit in the laptop even though the laptop is not on. Now I know the laptop detector is actually inductive amplifier which can be bought from electronic shop.

Courtesy - Meera Neelakantan