The KISS approach can be quite effective.
Fit a well hidden switch which isolates the fuel pump and the fuel gauge.
The scum drill the locks, disable the alarm and immobiliser, break the steering lock, flash up the motor, which dies after a couple of seconds. They then run down the battery before noticing the fuel gauge reads empty.
The down side is that once the battery is flat the alarm & tracker wont work and you will never find the code to reset the radio. Also it is not much good if they have a tow truck with them.
These oiks are so inconsiderate. When my Rangy was nicked, the took all the cash out of the ATM that they left in the boot, before dumping it.
You would have thought they would leave at least £100 for the hire of the vehicle.