I'm also interested in doing something along these lines.
This summer while on vacation in Colorado I threw my old laptop in my Samurai and starting hitting the trails with iguidane. It turned out to be a great tool considering I really didn't know the area, and didn't even have a paper map with me. I covered about 3,500 miles in 2 weeks and it was great. The navigation to a city didn't always take the best or most scenic route, so I sometimes ignored the suggested routes. On the trail I was surprised at how handy it was. I expected to just turn it off once to the trail, but I-guidance actually had a lot of the forest trails in its database. It allowed me to explore around a lot more then I normally would have on my own during mid-week wheeling (had the trails to myself).
Since then I have bought some better equipment, originally for the tow rig, but have been wondering about making it easily swapped over to the Suzuki or my rock crawler. Software is the key question.
I'll be checking out the Delorme software and see how it does. It might be good for the rock crawler.. But I think your tracking software might be the better choice. I'll play around with both and see where they get me.
I just know that I don't want to use my Garmin hand held any more! As a side note, I'm using one of the USB mouse receivers with the new chip set. While in the Colorado forests, the Garmin kept loosing signal and the USB mouse never had a problem short of tunnels (even held signal for a bit near the entrances of tunnels.)
I'll probably make my OLD laptop the 4x4 PC as it is disposable, my vehicles are both rather open, and get VERY dirty after a weekend of abuse. (Dry desert wheeling for the most part = lots of dirt and dust.) Not sure if I want to drop the touch screen into the 4x4's for this reason.
Please keep me posted on what you find.
-Wayne
http://aaaprodisplays.com/rotozuk/4X4.html