Now I am not sure what type of Linux that is on the Nxx. Is it possible to make program that work on a Linux laptop to work on a Nokia Nxx?

I was thinking about this TomTom Go Linux http://osx.freshmeat.net/projects/ttlinux/

I am still not sure what to choose between N800 and N810.. lot of rumors about maybe same spec processor and not.
If I could use TomTom software on a N800 with TomTom bluetooth gps receiver then I would maybe use that instead of the internal gps with other type of map software.

What you see there is just the gpl part of the tomtom (the kernel, cross-compiler, some utilities) and not the navigation software, so there's nothing really useful for the tablet.
http://www.tomtom.com/page.php?Page=gpl