I recently batch-geotagged photos of mine for the first time ever; I ended up using http://www.carto.net/projects/photoTools/gpsPhoto/, it is quite handy.
If you're planning to make an API I suggest you make it gpx compatible; in case you ever obtain anything that is gpx already, it would save you a headache.
(Oh, by the way: this entry was written by Peter Molnar, and originally posted on petermolnar dot net.)
