Some thoughts on the topic:
(feel free to take them worth a grain of salt)
You may wish to check out Dasher (http://www.inference.phy.cam.ac.uk/dasher/)
It looks rather silly, and is a bit awkward at first, but I think might be interesting as it only requires the joypad. It can be very fast (The webpage claims upto 39wpm), at least faster than I can type on a cellphone. The only downside to dasher is that it would probably require the full screen, so it would need to be toggled on and off. Dasher is under the GPL license (and has pda ports, so you could see how they manage to toggle it).
Also, IBM has quite a bit of research published about different text input methods. I do not have a link, but can find one if anyone is interested.
(feel free to take them worth a grain of salt)
You may wish to check out Dasher (http://www.inference.phy.cam.ac.uk/dasher/)
It looks rather silly, and is a bit awkward at first, but I think might be interesting as it only requires the joypad. It can be very fast (The webpage claims upto 39wpm), at least faster than I can type on a cellphone. The only downside to dasher is that it would probably require the full screen, so it would need to be toggled on and off. Dasher is under the GPL license (and has pda ports, so you could see how they manage to toggle it).
Also, IBM has quite a bit of research published about different text input methods. I do not have a link, but can find one if anyone is interested.