A quick addendum,
At a minimum, I would think that Latitude and Longitude, maybe also Altitude and Direction, should be Standard Library fields. If you are reading and writing the rest of the EXIF tag, then include these.
A lower priority, but something I'm trying to do at the moment, would be the ability to export to Google Maps/Earth (KML/KMZ files) as well as other map overlay formats.
Those are the basics. There are lots of things that could be done beyond this...
This will be an interesting space to watch over the next six months as Google, Yahoo, and Microsoft slug it out over local search and their competing mapping platforms.