I don't know about one that announces LoH or HotR, but I know that Tankadin announces when use use Divine Protection and when it wears off. You can customize the message as well. Also announces resisted/immune taunts and when Avenger's Shield misses, but really those are the most important ones anyway.
I also use TankPoints, mostly to make sure when I lose defense rating I'll still be at the defense cap, and I use PallyPower as I think every Paladin should. Most of my other addons are just convenience addons: AtlasLoot, Titan, etc..