car alarms

Hi gossy,
you will find that most alarms will have several areas of protection as standard. Door protection usually provided by direct hookup to door switch curcuit.
Add a switch to the bonnet if not supplied as standard. make sure rear door is on same curcuit or as above put in another switch.
You can add movement switches,glass breakage sensors, proximity sensors (useful in a convertable) There is a miriad off sensors available to fit and any good installer should be able to recomend a good combination.
you can remote start, remote electric window wind up sunroof closers.
Add a internal screamer siren to annoy hell out of the crooks.
Most good alarms will incorporate two/three immobiliser curcuits.
BUT, speak to an installer and probably best to keep it pretty simple if you are going remote, even then pretty well all immobilisers/alarms are pretty simple tp bypass if things go wrong.

Gossy
I would be cautious about an immoboliser with the alarm as outback workshops do a good business ripping them out when they buga up.
Ian

Another thing to consider is for you to know how to disconect it if need be. My key fob thingy recently got moisture in it. Hence would not unlock doors, turn off alarm. Ignition would not turn it off either.
Ever been under a bonnet with a siren going off?
Just as well I had the actual siren key, and knew which wire to disconnect.