It lets you pick a photo you took (or that someone sent you) and then points you in the direction the photo was taken, kind of like a compass, based on the coordinates stored in the photo's EXIF data. It's basically a fast and easy way to mark locations and get back to them.
Originally I tried it in JavaScript, but iOS strips lat and lon info from photos when they're picked with a file input field. You can still find the beginnings of my hacked together JS version here: http://foodsfofree.herokuapp.com/
This is just a side project I built for fun since I hadn't built an iOS app before, so I'm not trying to turn it into a business or something, just wanted to share it!
You can also read more about it here on my blog: http://gohnjanotis.com/photo-find-v1-1-released/