Here is a Youtube video in which a gentleman by the name "Coltstatus" (thanks for the video mate) installed one in his car and shows how it works. I'm contemplating on getting one myself. The only problem is it would be coming from Australia of course. Not so easy to just go out and buy one.
If you click on the "I agree" the video will play inside the window here in this thread but here is the actual link to the
Adaptronic Vidigauge on the Youtube website.