Too much protection never hurts, but this protection has to be somehow cost effective. Sometimes simple solutions can do great. Car alarm system doesn’t always help especially if someone got your keys with remote. The only hope is left to immobilizer, well if you have one.
This is a pretty simple immobilizer built on PIC12F629 microcontroller and ID-12 RFID chip. What it does is cuts car ignition with relay and turns on only when correct RFID tag is read. So no one apart you will be able to start your car even if alarm is unblocked. Just be sure not to carry tag along with keys.