A little while ago we wrote about the bolt-on GPS units for Nikon cameras, which’ll allow you to geo-tag all your pictures. Provided that you use a Nikon, of course. Now you can geo-tag your photos whatever camera you use. Provided that you have an iPhone.

gps4cam is an app that you download to the iPhone for $1.99 and to your computer for free (you need both bits), which then allows you to geo-tag your photos when you stuff them into software such as Aperture, or iPhoto, or Picasa.

The really, really good news about the iPhone app is that it doesn’t require a connection to function. You turn it on at the start of your trip; at the end of your trip, you press the ‘export’ button to generate a QR-Code for the trip and take a photo of the barcode that shows on your iPhone screen. Then you upload all your photos with the gps4cam software and taa-dah! Geo-tagged photos.

Much more detail available from gps4cam.