i use a few different brands of car security in my workshop and i think that the Mongoose M80S is about the pick of the crop at the moment .
these have 3 point immobiliser , security housing , all black wires etc.
should be able to get one for around $500 fitted.
there are other systems that have more bells and flashy bits but they mostly are not as good at securing the vehical.( the main aim of the project )
what ever you decide on, i would insist on an Australian Standards approved system . there are a lot on the market that dont come even close to meeting the Aust Standards. even some of the big brand names.