I'm considering building an auxiliary unit that interfaces with the EFIS (and maybe even the EMS) which runs on a laptop, and outputs to one of the in-car DVD screens. I've found one with similar specs to the 7" D100 screen, which would work quite well. If I do end up developing it, I'll post the results here.
The whole system, incl laptop and
screen can be assembled by anyone who is capable of installing the efis/ems and would probably cost around R6000, or about $500 (depending on what laptop you can get hold of).
Then you can run GPS software (like Fugawi) on the laptop and have a full moving map, as well as having the logging capabilities, winds aloft, Flight Director, etc. etc. all on a small screen.
I'll keep you posted on the developments.
P.S. this may also be a solution to those who are having problems with the depth of the D-100 - some of the in-car dvd screen are very slim, and most of them accept a video input, which most laptops can supply.