There not Aus approved therefore insurance company will not cover your alarm as part of the policy. If they find out its a non approved alarm (like i know one person did) then kiss getting insurance anywhere else goodbye as well.
Viper to me is purely wank value and not really a great alarm unless your willing to spend $800 -$900 and upwards. Dont get me wrong protection is important for ya ride and worth every penny, but there are pleny of alrams out there (australian made/legal) that will do the exact same job and for half the price.
Look at Cyclops, Vision and some of the others that you can buy locally. Talk to people in the business (CHris Rogers aka Audio Express) as they are always willing to help you out and steer you in the right direction. I didn't even buy my alarm from Chris and he gave me a phone call and helped me out and we live at the other ends of Austalia. To me that is a guy that cares about his job, know's his stuff and is willing to give up his time and knowledge to help out fellow car enthusiasts, we need more of these people and there are plenty of them on SAU. Look around and you will realise you can get a better alarm and save yourself a few dollars along the way. Think of it this way, the money you save on the alram itself, you can put towards a professional install. My 2cents anyway