[Baertram]

Building a notification is no problem, I know that. But how do you trigger it? It shouldn't be manually as Wambo described but done through something that happens during boss fights e.g.
He does not like to see by himself that something happens, press a key then to start a timer.

Therefor you need the addon which is able to define the circumstances (buffs e.g.)
So why create a new one when an exisitng one already provides all the "trigger configuration"?

And to be honest: Users who think about such possibilities like wrning during boss fights etc. will also use such kind of configurable addons.
If you want to have something very easy to use for every player type, beginner and experienced, there won't be one addon which fullfills the needs.
That's why Wambo asked for the "shareable" rules I assume.