Not sure why you would want to get into hardware. Current tablets are commodity driven, low coast & lower profit.
If you are hardware bound, you will compete with the likes of garmin and several other world class GPS manufactures.
Software: Google Maps, Has all the maps with intregrated sat images. It will do car, bicycle, taxi, bus, & walking routes. (I have used the bus & walking routes in London)
You would only need tune the macros to your taste and you would have a package that does any platform. The big pos?? The updates are free and it's platform independent..
My $00.000002