A fairly simple addon that can play a sound and give a text or icon warning whenever important talents or abilities proc, or you gain certain buffs. Most important procs I could think of are included by default, but more can be added or removed.
Icons for abilities which are off cooldown can also be shown, as a visual warning that said ability should be used immediately.
When adding a buff or spell to look for, remember to use the exact, case specific name.
To use your own sound, add the file to the Interface\AddOns\Alert\sounds directory, type the file's name in the edit box in options, and choose custom under the drop down menu.
Please report bugs and comment with ideas for changes, additions, or improvements.