Gadgets Aggro is about the closest you can get Tanivia – it will bring up an on screen message showing if you have agro or not.
Very limited as the Rift API doesn’t allow much, so as a tank you can’t tell if you loose agro from one out of a group of mobs, but for a dps it’ll at least show you that you have agro from something. No sound though, although that could be added.
BIS calendar to add to the list – it’s been mentioned elsewhere on the forum and is a really useful tool for notifying of events, the downside is everyone needs to have it installed to get full functionality.