If you start from scratch, aiming to create the most efficient possible thumb-chording that does not require looking at your SmartPhone, you can do a lot better than Braille. For example, let’s start with the fact that over 75% of all characters typed are one of SPACE,E,T,A,O,N,R,I,S,H,D,L,C,U (roughly in descending order of frequency).
We can use the entire SmartPhone screen to lay out a 5×3 thumb keyboard with the following arrangement:
| E | U | C | L | T |
| → | O | H | S | → |
| A | I | D | R | N |
This keyboard has already taken care of more than 3/4 of all the characters you’ll ever type (we include two ways to type SPACE because it’s by far the most frequently typed character).
We can then get an additional 75 additional characters by “chording” with both thumbs at once, with the left thumb on one of the three left-most columns, and the right thumb on one of the three right-most columns. 75 characters is far more than needed to type all the letters, digits, punctuation and special characters on a keyboard.
I think this keyboard is going to be very fast to type on. Since all the other characters after those first 14 are used much less frequently, having them as two-thumb chords won’t slow you down very much.
Not only does this arrangement allow non-sighted people to type quickly, but it can also be used by anyone in a situation where you need to type quickly into your cellphone without looking at it (eg: during a meeting).
As is usual for keyboards for the non-sighted, there would be a tutorial mode that allows you to drag your thumbs over the keyboard to sound out each character.
I suppose this is a solution to your problem of writing in a darkened theater as well. No need for much glow to come from the screen if you don’t need to look at it. Is that what got you started recently thinking about the issue of typing fast for non-sighted people?
Actually it was a complete coincidence. These last two posts came about because I’m on the thesis committee of Nektarios Paisios, who is a non-sighted Ph.D. student in our department. He was showing some input techniques for SmartPhones that he had created for non-sighted people, and I had through the years done research on text entry for PDAs.
Although there may very well have been an unconscious connection in my mind between the two topics, considering the timing.
It would be interesting to see how willing people are to learn a new chording keyboard. I went through several generations of Palm Pilots back in the day (got my first one in 1997). I liked the Graffiti input, but I think many people were adverse to learning it. And Graffiti was much closer to normal writing than your chord keyboard is to normal keyboards. I suppose Graffiti is too slow to satisfy your fast-typing needs, but I think it can be done without looking at the screen, especially if the whole screen is the input area.