Software is the thing. Most of the pseudo Tech 2's are based on ELM chips, will communicate with the car ECU, but its knowing what questions to ask. There are a standard set of responses that each manufacturer is required to adhere to, but a lot of 'manufacturer specific' queries. The cheap Pseudo Tech 2's tend to have free/shareware software with them that can give the standard responses, but they are not written with Vaux in mind, so its very unlikely that you will be able to cmmunicate with the gearbox ECU. There are a couple of russian systems out there,
http://www.opel-scanner.com/opelscanner.html that seem able to comunicate with a lot of the car functions, I suspect the programmers have access to a real tech 2 and have monitored the responses. The USA are moving forward here, it seems there is a law that allows the manufacture of alternative programming systems so that small garages over there can reprogram ECU's without buying an expensive Tech 2. For example
http://www.drewtech.com/products/mongoosevpw.html . It would be nice if it works, it would have saved me several hundred £ recently if I had access to one but......