I genuinely think that a better solution is to buy a phone with T9 if you have input problems or like to enter stuff when not looking at it. You simply NEED a tactile interface to do that effectively.
I carry a Nokia 3330 and Lumia 710 around. The 3330 is still a thousand times easier to enter text messages into. I can use it with my eyes shut and make absolutely no mistakes. The 710 however, is painful to enter text into.