After a quick search I did find an app for iPhone and Android -
Geotag Photos
It works by recording your location on your phone at an interval that you choose. You then sync the log on your phone with the pictures taken using their application. Exif data is merged based on time. As long as the time and date on your camera is correct you shouldn't have a problem.
This might actually be more practical than the solution I was thinking of before. This way you're not draining battery power on the camera and phone by maintaining a connection between the phone and camera, and the phone and GPS.