Dont buy tech 2, you can get USA tech 2's, or even European Tech2's, the Aussie software wont work with there, and if you manage to get an Aussie Tech 2, the software only has a short life span, and Unless you are a holden dealer, you cant get the software. And even without security approval from TIS you cant access some features on the newer cars.
If you want to purely access DTC's and view live data, I have made my own OBD2 compatible scan tool that cost me less than $300. It has the ability to read all the OBD2 protocols and can read CAN BUS with out a CANDiBUS adaptor, which is handy if you want to access new opel based cars or VZ's.
I cant find the exact site for this interface module but here is the address on the assembly manual.
www.ozenelektronik.com
Otherwise there are many other scan tools available, and much cheaper, the best I have used is the Scanmaster pro which is a Scan tool as well as a Scope which is great for diagnosing problems. It is compatible with many diff cars and is around $4k.