I do a lot of landscape photography and often get a bit confused as to exactly which images go with which waterfall. Geotagging provides a great solution, but it's not worth it to me to lug another piece of equipment, let alone buying a separate unit. Now there's an inexpensive and very accurate solution. It's called the smart phone.
GPS4cam is a small app you load onto an Iphone or Android device. When you start a trip, you turn it on, select the interval at which you want it to refresh your location, and fire away. You do not connect your smart phone to the camera. There are no wires, no bluetooth connection, just an app running on your phone while you go about your work.
When you return home, you export your trip information into a 2D bar code, then take a photo of that code, as shown on the left.
You load GPS4cam's desktop software program (Mac or Windows 32 or 64 bits) and run it against the folder that contains both your images and the picture of the bar code. (You either download your photos to a temporary folder or connect your camera to the computer and do the file processing on the camera's media card.)
Once the software has appended the geotag data into the metadata of each image, you import your files into Lightroom, Aperture, iPhoto, or any other imaging software that supports geotagging. As soon as the images are imported, the location of each image shows up on your map.
I set the refresh interval at 5 minutes (there are also options for 30 seconds, 30 minutes, and manual) and took test shots immediately after getting out of my car. GPS4cam accurately identified with every image was taken. The only cost was less than $3 to purchase the software (you read that right) and a bit of extra time, which will vary depending on how many images you have to process.
If you're not yet using software that supports geotagging, you will some day, so even the casual photographer might want to consider spending $3 and taking the time to process their images with it. (I wish I had had this app with me during my trip to Tanzania and have many shots taken over the past dozen years here in the Northwest that would be of commercial value now if I knew precisely where they were captured.)
It is not necessary to sync the camera's time to that of your smart phone. Anything approximate seems to work. You can read more about it on the developer's website.
It's a nifty app that works exactly as advertised, and the price is almost too good to be true.