I think this laptop detection device is a myth
If you dress like an office worker, you come out of your car and don't carry a briefcase or bag with you, then chances are your bag is in the car boot. Thieves can easily make that assumption and try their luck. Or maybe you stopped the car then put your laptop in the boot, lock your car then walk off. Thieves also can see that.
if you ask specifically for 'laptop detection gadget' then of course it doesn't exist..knowing Malaysian creativity,everything has got multiple purpose..
So instead,try to look for 'frequency scanner'..