fperkins.com

1. Go to your /Library/LaunchDaemons dir
2. type: sudo pico com.fperkins.isightcapture
3. Put this in the file:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN"
"http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Label</key>
<string>com.fperkins.isightcapture</string>
<key>OnDemand</key>
<true/>
<key>ProgramArguments</key>
<array>
<string>/Users/Frank/Scripts/screenCapture.sh</string>
</array>
<key>StartInterval</key>
<integer>60</integer>
</dict>
</plist><

4. Load your job by typing: launchctl load com.fperkins.isightcapture

Of course, change the name of the file to something that makes sense to you and also change the ProgramArguments to match the script you use. For this script, it runs screenCapture.sh every 60 seconds.