I have a Galaxy Tab 7 inch with Air Nav Pro.
It works okay as backup or so but not 100% reliable.
As said above, wait for the Ipad mini.
I wish I'd done that actually...
is it true that all external used equipment like GPS needed an approval from JAR??
that means, putting your iphone with navigation app on the window is illegal???
As long as you dont drill any holes or fiddle with the wires, you're fine.
FTF