I honestly can't imagine trying to do what you want that way. The units like the Traqmate and Race Tech DL series use accelerometers along with the GPS to get the data they get, and without the accelertometer portion, your data isn't going to be very good at all. Combine that with the fact that I simply can't see a PocketPC lasting long in a race car environment, and I think you have your answer.
I've used a Traqmate and it was okay, though not great. The biggest drawback for me is that you either have to hook a laptop up via a USB cord basically to the cockpit -or- remove the brain to download data. It's also limited in data amount to just a couple hours at reasonable data rates, which I also don't find acceptable. Oh, and it the one I used had a very stupid "feature"...when the memory *did* fill up while on track, the display just went to "MEM FULL" and wouldn't keep at least giving me cockpit lap times. Very stupid.
I've got a DL1 on order, which I understand also has a couple of annoying shortcomings (though I'm not sure what they are *yet*). But it does use CF for storage, and a 2G CF will store three days of data, so it should handle a complete 13 hour enduro at VIR.

Plus you can yank the CF and swap it quickly if you want your data but don't have time to download *now*. Also, and this is the best part, the DL1 works fine with autocross whereas, at last check, the Traqmate did not (though they are promising support, they have been for months).
Sorry to hijack the thread further. For a car NAV system I prefer my Garmin GPS-376C. But I use it for boating, too, which is a plus over some units. I like the size and the interface. The screen is nicely outdoor viewable. It also has XM built in, which is nice for trips...but the best part is that if you're willing to be raped for $30 per month, you can get weather data overlayed on the maps that's up to date (including radar loops, forecasts, temps, etc). Of course, at some point you're gonna be able to combine your laptop with a USB GPS (like the one mentioned above) *and* connect to the Internet via your cellphone or data card or wifi or whatever and download that same weather data to your GPS app. Eventually.
--Donnie