** CAN BE USED WITH DSLR's **
I was about to spend £50+ on a GPS logger that does this. So to me its a bargain!!
Basically this is an app which logs your iPhone GPS position, you then download the data with your pics to the downloadable software for mac/pc. The softawre will then GeoTag your pics, ready for you to use and edit in whatever software you prefer.
It's really easy and simple to use, great for anyone who likes photography. http://www.geotagphotos.net/en/
Works with RAW file types.