I bought my car from a dealer + when he explained the security in the car he said he'd left the stock immobiliser in + added the proximity sensor immobiliser as well, giving me 2 different immobiliser setups...
If I don't hit the 'unlock' button on my key remote, the car won't start. It'll keep turning over, but refuses to start. It self arms this as well. If I turn my engine off + don't lock the car, I still need to hit the unlock button to disable the security + start my car.
And of course if the proximity sensor isn't next to the ignition, the car won't start.