I’ve been searching for an easy way to trigger my Canon DSLR from my Mac and found this one: The DSLR Camera Remote Control by ononesoftware. All you got to do is download the iPhone or iPod touch App and the DSLR Remote Server Client. Then  you connect your Canon photo to your Mac or PC via USB or Firewire start the DSLR Remote Server Client and the iPhone App. The Computer and the iPhone have to be connected to the same WLAN network. Now you can trigger your cam from everywhere you want and even see the result immediately on your iPhone screen. If you purchase the DSLR Camera Remote Professional App you can even control shutter speed, aperture and white-balance. It’s a really great way to set up and control a shooting perfectly.