Cannon shots are being fired every 30 minutes at the military base near our house. It surprises the shit out of me, so I wrote a cronjob to warn me of incoming shots:
0,30 * * * * echo "Incoming cannon shots in 30 minutes." | say -v Vicki 29,59 * * * * echo "Incoming cannon shots in 1 minute." | say -v Vicki
I didn't know Mac OS X speech synthesis feature was scriptable!