yrs ago ive heard tat they are using a device as small as a car alarm remote tat will detect emittion from the laptop battery.....

wat happens is tat when ur laptop battery is attached to the laptop it'll emit some sort of radiation or something like tat which is totally naked to the eyes

this device will detect these emittion hence even when u hide it in ur vehicles they will still know ur laptop is there

so u can either remove the battery or dont leave it there