There are a couple of issues with any of the tracking devices, the first is that police forces have openly said that they don't have the available resources to jump on a report of a tracker equipped vehicle theft so may well not find it if they don't have the manpower available. The second is that the determined thieves quickly get the vehicle enclosed in a full metal box (normally a shipping container) which blocks all radio frequency signals. They then have all the time in the world to move the container so that the trace leads to a dead end and while the vehicle is in the container, they can find and defeat the tracker. High end car theft is a well organised affair and compared to the money they make, the cost of a truck and container is very small.