Originally Posted by Daniel_

Most cars on the market in Europe don't seem to bother with alarms any more, but imobilisers are very common.

My car (a very ordinary and cheap 2000 vintage Renault) has a device in the body of the key that trips the imobiliser and allows the engine to run, but fire the car up with the wrong key (even if it is cut correctly it needs the right eectronics in it) and it won't even turn over. The entire EMS computer stays asleep.