Being a Nokia user for almost 10 years, moving from a T9 keyboard system to a full android keyboard is something I find really hard to adapt to. The reason why I prefer the T9 keyboard over a full keyboard is the ability to type using one hand, not to mention the buttons on a full keyboard is simply too tiny, I tend to press on the wrong key once too often.
Upon researching, Smart Keyboard Pro is the best T9 keyboard for android. It is still somewhat clustered with additional keys, none the less it is still free, almost as good as Nokia’s keypad. Head over to Google market place and download this app, it is free.
(EvenBetter)NumberPad on the other hand is the closest thing to Nokia’s T9 keypad. However, it cost 3.99 USD.