Kevin writes - "I have been searching for a good way to connect a Nikon D200 to a GPS in order to geocode photos. I have not found a solution that I thought was near a reasonable price. I have therefore made my own. I made a project page for it and posted it for all to see and replicate..." [via] - Link.
Related:
http://blog.makezine.com/archive/2006/08/how_to_make_a_nikon_d200.html