Every single time I've seen a car alarm go off, it's been with the owner, or it was a false alarm and the owner was too damn far away for anything to be done about it.

I've experienced the shock of having my rental car burgled outside Marseille en route to Aubagne in less than 5 minutes, as I stepped in and out of a store, and this was a new Citroen with a fancy proximity based "secure" lock - the alarm system was far worse than useless thanks to the false sense of security.

There's a lot of research happening into defeating wireless locking systems, and the security systems even on the high end BMWs are abysmal.

I'd much rather simply lock it physically using my key and shut off the alarms.