If you read the linked article, aside from the very beginning, he uses Sleepwatcher [1] to trigger an Automator script that launches Photo Booth and does the 3...2...1 countdown.
[1] http://www.bernhard-baehr.de/
[2] http://www.apple.com/macosx/what-is-macosx/apps-and-utilitie...
[3] http://www.apple.com/macosx/what-is-macosx/apps-and-utilitie...