Once, when away on a trip I was horrified to find that
a) I'd left my alarm clock at home and
b) 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.
That was me - I was particularily paranoid about seeing a heart beat. The current version calculates the delay, reformats it as hours and minutes(for idiot proofing) and pops up a TK/TCL window to grab my attention (in case the volume is down)