As I went to bed last night, it was stormy out, and my power went out four times before I actually left my desk. My video game time thoroughly interrupted, I wanted to be sure that I was going to wake up in time for work in the morning. There are plenty of shareware and freeware alarm clock programs out there, but as far as I know, none will work if the computer restarts after a power failure.
You can probably do this trick alone with iCal, but I wanted to find a solution without setting up a multitude of calendar events, and I don't know iCal as well as I should. So I created an Automator application to 'Get specified iTunes items' and then 'Start iTunes Playing' (both in the iTunes library entry). I picked a playlist created with a few songs to be somewhat obnoxious, so that I'd actually wake up, walk over, and turn off the computer. I saved the workflow as an application and stuck it in ~/Applications/.
Then, I went to the Terminal, and elected to edit the crontab (via crontab -e). I added this line:
0 6 * * 1-5 open ~/Applications/alarmclock.app
Just make sure that you've enabled 'Restart automatically after a power failure' on the Options tab of the Energy Saver system preferences panel. Incidentally, about 10 minutes after I finally went to bed, the power went out again. It didn't come back on while I was awake, but I woke up on time.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20051108062925355