The Auto Whiner alerts you when stuff happens in raids/parties. Examples:
* A priest tries to Mind Control a mob, but it's immune
* A rogue tries to interrupt some important thingie with a Kick, but the mob parries.
* A mage tries to polymorph something, but the mob resists
* A druid enables Frenzied Regeneration, cool, he's in imba mode now
* A warrior enables shield wall, cool, healers can slack now
* A druid innervates someone, yay.
* A paladin taunts with Righteous Defense, but the mob resists (shit, stop dps so he can get aggro on it)
When this occurs, you'll get a cute, friendly, big, flashy alert all over your screen (configurable to be less big and less flashy), telling you what happened.
These are a few examples. Warlock fear/banish (zomg I forgot to add seduce, will add), priest shackle/fear, warrior taunt/mocking blow/challenging shout/last stand, shaman earth shock (the spell interrupt part) and mana tides.. Everything you need to know which the default UI doesn't tell you.
This addon used to be called Meat Shield. It was for tanks. when you got a taunt resisted or enabled last stand, it yelled in party/raid/rw/say/yell/wootevah. This one is "silent". It alerts yourself, locally, on your screen, without spamming any public channel. Kind of like a boss mod, only for stuff like mentioned above, not bosses.