This is sort of natural think to come out next: Mobile GMaps - Google Maps and MSN Virtual Earth on your mobile phone!. Only one problem remains to be solved: the price of data transfer to mobile devices. Can you say Wifi? Can you say Wifi when you are lost?
I wonder how much money people would pay to know their way. I bought a navigation system to my car after getting lost too many times. Having a Female domina in my car telling what to do is sort of nice. She speaks even Finnish. And the best thing; when I get bored with her, I can shove her into the glove compartment.
Having just a map in my pocket simply isnt enough if I dont where I am... or maybe i could stop bitching and walk to a street corner and type those two streets to my mobile!
Mobile phones have a color display and new models have speaker phone that can shout instructions. Think about a service where you could reprogramme your navigator to have personalized instructions. "Stupiiid! You should have taken the previous left turn."