Disturbing moral and privacy implications asides, this technology simply doesn’t exist.
At Multimap we enable companies to track their vehicles on our maps. However in order to get the location out, a mobile phone connected to the car battery needs to be inserted in the boot.
While a phone is not strictly necessary, the upshot is that you need a powered GPS device that can transmit its location. While this may fit in your pocket, it will certainly not fit under your skin!