I looked into the Ghost system when I got the E which does not have a switch off keyfob, it costs £500 plus installation if you have it done at home. The pin sequence is actually some button presses you program yourself, eg stalk, windows, radio etc, without which even a cloned key or OBD hacker cannot start the car, it can only be towed away. There is a simpler mode you can set for eg servicing without the full code revealed. There are some reports of problems with some cars, I suppose the least popular ones where they do not have a lot of experience with the canbus system. The idea is so good it is a wonder car manufacturers do not build in something similar with all the publicity about keyless thefts.
At the end of the day a faraday pouch was cheaper.