It depends. If they have to come onto private property to install the device, they have a problem if that area is within the curtilage of the dwelling and they don't have a warrant. If they install it on the car on the public street, no warrant is required. Of course, if you find a foreign item installed on your own car, you can smash it to smithereens and no body can complain, because it was an invasive item on your person property, like a wart on your finger!