Photo Geolocation scans a folder you choose for photos that contain geolocation data and displays the photos as well as their location on a map. You can even specify a specific location on the map for searching purposes.
Ever wonder where you took a picture? Now you can easily scan your geotagged photos and find the location. Suppose you take a lot of photos with your iPhone or other camera that geotags the photos. You know you should, but you don't bother giving the photos names or put them in a nicely labeled album. Instead you just feed them into iPhoto or some other folder. Eventually you end up with a lot of unnamed photos, over 10,000. Now someone says, "let me see the photos of your Yellowstone trips." You could search all 10,000 photos, somehow flagging the photos you think are from Yellowstone, but that might take some time. Instead you use Photo Geolocation, set the filter map to Yellowstone, and within seconds all your photos of Yellowstone appear! Or use it to simply browse your photos!
Note: you cannot change the geolocation of a photo with this app.