The Teleport has a cooldown, but its up to them whether or not they want to use it right after it cools down. A mod for this would be hard to right and probably would only be able to tell the exact instant they teleport and not any kind of warning (maybe a Teleport Incoming! thing after 30 seconds or so, but thats it).
Once you've gotten a few solid attempts in you can get a feel of when the teleport is coming and adjust accordingly.
The main issue with using a mod on this fight (and I suspect a mod on Ouro, too), is the room is so big, and the combat log range is 40yds. I had made a mod for us, but it ended up being that I was out of range of the combat log message 50% of the time, so it was very unreliable. Ended up using a Timer mod instead, and manually resetting it after every port.
And as for:
The Teleport has a cooldown, but its up to them whether or not they want to use it right after it cools down.
This is true for any of the numerous mods on abilities like Wing Buffet, Chromaggus Breath, etc. The timer can give you a heads up that the next one is happening soon, but it's never going to be 100% accurate.
Unfortunately we haven't gotten to the Twin Emps yet, so don't want to delve into this any further than this thread has already spoiled in order to deal with the queries. But once we get there, I'm sure Limited will work something into the mod - while it may not be pinpoint, it should give a general indicator (much like solid experience with the encounter, I assume).
I usually just use macros to make the calls, its pretty easy to do with Chronos (search for it on curse-gaming if you're interested). Hit the macro after each blink and it will announce it x seconds after the blink that the next one is coming shortly.
/in x /rs Teleport Incoming!
It's definitely more work than running mod, but it's less work than using a stopwatch, and its quick and easy to tweak around with if you're still in the learning stage of the fight. Just gotta change one number in your macro settings to change the time on it.