For $250 I dont think youll find a pager system (unless you can install it yourself).
You might try www.dynamco.com.au, they could point you to an installer. I had the P785 done for $440 installed which is basically their top model. (Diagnostics, transponder type (walk up immobiliser off, walk away immobiliser on ), 2 point immobiliser, backup battery alarm, etc... ) Black wiring is basically standard on every alarm system these days.
For $250 you might be able to get one of their immobilisers installed because their cheapest alarm system is approx $300 installed. So basically it depends if you can / want to do it yourself on what model you can afford.