Combat Log Scanner watches your combat log for SPELL_CAST_START events and notifies you if if finds a match with a per character supplied list of what you want to watch for.
The notifications are a sound is played and output is sent to MikScrollingBattleText if it is installed
To use a custom alert sound just place a file called alert.mp3 or alert.ogg into the addon directory before you start WoW
for mp3 type "/cls custommp3 on" for ogg "/cls customogg on"
"/cls" to access commands