Hmm. Interesting. I'm technically challenged so don't know if it's already being done (aside from gps systems). I know I once worked at a job where the drivers (cable installers) constantly called me at the office for directions. They had maps (usually) but sometimes just couldn't find the address. So I'd do a quick mapquest and get them to their destination. They weren't equipped with gps yet.

A little more research should tell you (or anyone else) if it's a viable idea.