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...

The first day or two it just took the photo in the background without me knowing about it. But too many of the photos were really bad (deleted most of them). I was moving or my head was cut off or out of frame. I was willing to trade the 'security' of hidden photo gathering and instead just had it launch PhotoBooth and immediately take a picture. That gave me three seconds to compose myself and if I couldn't do it in time I could just click the capture button and take another one. Occasionally I would get annoyed at it, but it was over quick enough.

He mentions an automator workflow and sleep watcher, doesnt really give any explanation on how he really did it.

I tried playing with recording and automater, but it wasnt happen about photo booth.

You could just add a growl notification, might get annoying over time though