I'm glad you asked, because I've been buy wow gold in the market for an addon that does this as well. Now that it's legitimately important for Shadow Priests to have Inner Fire up 100% of the time in a raid setting, my inability to babysit that buff is really coming to light. I was pointed in the direction of SmartBuff by a friend, and it was also suggested in the comments after you asked this question, so I'm going to give it a shot.

Looking at its description on Curse, I probably won't use most buy wow gold of the mod personally, but it looks just like what you want. I'll likely just use the alerts to let me know when to recast Inner Fire and such. You'll probably use a lot more of what the mod has to offer.

I know, it looks like a real copout when I completely ride on the buy wow gold suggestions of others and don't have much personal experience, but it's a learning experience for both of us! It's like a bond, slunk. We're soulbound.