I don't know if they were ever released (probably not), but there were certainly plans. If I recall correctly (again, probably not), ATI wanted to include a new port on high end laptops that would basically serve as a hook up for an external gpu (there would also be an internal gpu). I remember the claim being that it would be close to PCI express speeds. Now, what I don't remember at all is if the signal would then be routed back to the laptop or if you had to use a separate monitor. I do know that a working model was present as some trade show (CES?) a few years ago, but I haven't seen anything since that story on Digg....I also don't know if that was the ATI solution or something completely different.
That said, when I was looking for a card a while ago, I didn't come across anything external while looking at sites, so I'd say they either decided it's not feasible or it just isn't ready yet.
