I depends on what you're trying to achieve. If its just mapping then lat, long and maybe altitude is all you need. The big thing seems to be how often you sample these points (currently once every 100 metres.)
If you're after traffic reports, as some suggested, then some kind of real time update and speed collection would be required. All doable in my app but adds complexity, cost and not much benefit until people are really using it.
Other important data is the street data, road names, numbers, speed limits etc. I have started research on this and will be coding once I've made the tracker robust and easy to use.