Yeah guys. You plug this thing in then run the "Select Monitor Dump" program from VWRX.com to get your ROM ID. Then you open up the SelectMonitor.ini file Phil made, changing the ROM ID of his SVX entry to the one that you just found. Run the SelectMonitor program and bam, you've got gauges/info!
But be aware that at the moment, the software is very buggy. It has a habit of locking up when switching between gauge and graph mode, as well as falling out of sync with the ECU as it attempts to update values. I have asked questions about this in the official forum but it looks like the creator has vanished. So I don't know if the software will ever be updated to fix these problems.
However, the Linux-based software that Phil is working on seems most promising. It cannot do what VWRX's can at the moment (all it can do is dump data from the ECU and TCU), but the actual communication code is all there. The ability to display incoming information as a graphical representation is merely left to be coded. And since Phil is an active member here who is very much interested in the project, his will be the way to go in the future.
It would be very cool for more programming-oriented people to get their hands on adapters. A joint programming project would be awesome.
Heck, I'm tempted to try my hand at a Java program or something.
Anyway, that's the lowdown. These cables allow you to connect a computer to your car and read information from the ECU, TCU, ACU and possibly other computers in the car. The actual software to make sense of the data is somewhat available but not perfect.