Source code?
Once, when away on a trip I was horrified to find that:

1. I'd left my alarm clock at home and
2. the one in my room looked, well, really ill.

So wrote a snippet which fired up the CD in the laptop. It was a simple loop which calculated the time-delta, slept for half of it and fired up the CD if the delta was less than 1 minute. Leave the volume up and something suitabley LOUD in the disk.