Sorry guys, but most of you are missing the point, by the sounds of it because you have never seen or used a predictive T9 implementation on a touchscreen device. And there's some hostility too, which is weird considering we are talking about personal choice and preference.
Anyway, for a start, you don't just get 9 keys! Space, caps, symbols and other stuff are catered for very simply using the fourth row of 3 keys.
You type maybe three or four characters and up comes a complete word, based on popularity and dictionary modifications. Hit a key to select the next word in the suggestion list, space to accept. If you run out of suggestions before the word you want appears, it automatically goes into "learn" mode and accepts whatever word you complete typing into the dictionary for next time. Shift/caps is a separate key, symbols are usually accessed from "1" which does not corespond to a letter. With a touchscreen, you can go back to and change words you have already typed in exactly the same way as you can on the iPhone. Just tap them. Basically, a current predictive T9 implementation, eg Nokia N8, outperforms the qwerty keyboard considerably. There are less and larger keys to tap to type a word. It's that simple.
I'd also debate the fact that T9 is redundant now that we have qwerty on a touchscreen. Qwerty was invented to stop typewriter keys jamming by specifically keeping the most commonly used keys furthest apart! How redundant does that make it? It's about popularity and what people are used to (in both cases), which actually makes no sense when you are completely changing form factor. But at the same time people *are* used to T9, so why not allow us the option?
And as for one handed typing not being a good idea? There are plenty of situations where having a free hand is useful and not taking your concentration away from whatever it is you are doing. Keeping control of small children for one, or carrying bags.
All this is beside the point though. Apple will do what Apple wants, and unless they decide that a keypad style text entry system will make thier device more popular, we won't get one without a third party app and possibly a jailbreak.
So, back to the OPs OQ. Is there a T9 style keyboard anyone knows of? Or any developers out there interested in making one? There would be a market for it, I am certain.
Richard