Suggested Developer Reading
This project interests me, as a developer and mobile computer enthusiast!
Upon a quick search, I've found a few resources which seem to be giving me a better grasp of what all this project(s) is going to encompass.
To start off with, the general direction and information is located in this thread.
Open Source Mapping
OSM Wiki Beginner's Guide to Mapping
NMEA Data -- National Marine Electronics Association.
Mods, feel free to add/remove/alter anything to this post if need be, and I don't get to it first.