I found out that there is a application called NAVIT that can use Garmin maps on tablet.
Since I do have some Garmin maps already that could be very interesting application to be tested.
The application itself can be found from here . It seems to be already quite old, already compiled March 2008 but this could be worth of waiting.
You can find more information from Internet Tablet Talk forums. That's where I found it at the first place.
It even looks like there is a newer version of application available trough forums.
Also some related pages: