Buy one. Simple as that we just finished a 7000km trip Darwin - Port Lincoln - Adelaide and the usual tourist stuff. Even my 19 year old daughter watched it, but it was a god send for my partners 8 year old.
As with many of the comments they are only used to stop the kids going troppo, otherwise eye spy, what am I, etc. BUT that takes a bit of effort when I just want to drive and concentrate on that, so yes I have no problems with one.

