This app is just brilliant. I took my new Canon 7D out for a spin around Hyde Park yesterday and wanted to track my movements. gps4cam did an amazing job. You literally just open the app when you want it to start recording your whereabouts and it'll take a GPS reading every 5 minutes (or more/less frequently if preferred). The app runs in the background and had only a slight noticeable effect on the battery life.
At the end of your trip, you simply tap Export and it'll display a barcode which you snap using your digital camera. The idea being that one of the images on your memory card has the barcode shown, which is then picked up by the desktop app. The desktop app (Mac & PC) scans through the images, gets the location data from the detected barcode, matches up the time each shot was taken with your corresponding coordinates and voila! your images are tagged!
Brilliant if you ask me. Here's a quick screenshot from within Aperture using the Places feature:
http://cl.ly/2P1u2g1y310w3n2z2T2J from this trip:
http://www.flickr.com/photos/lcooperdesign/sets/72157625581556748/Even if you don't use Aperture or iPhoto you can see from my Flickr page how the site picks up on the coordinates too. Awesome.
The only downside for me so far is the time it takes the desktop app to scan through and detect the barcode shot. Seeing as it's likely to always be the last shot I take I think it should find it quicker or give me the option to specify. I'm sure this is something that'll improve with time however.
All in all this is a highly recommended app!