Would you consider using a gamepad a possible solution? Maybe specialized hardware further down the road but ATM I think that the market forces have optimized the devices sufficiently.

The reason why I am asking is that I'm doing some experiments on making them usable for productive purposes. While practicing I noticed that my posture improved automatically. See you are sort of automatically drawn towards the keyboard giving you a Mr Burns like posture. As if there where a gravitational pull in the screen.

As I was discussing this with another person online I realized that it might be of use for people with wrist pains as well.

My reasoning is this, bear in mind that I am by no means well read on biology but I think it might be given some thought. While using a keyboard you are forced to a certain plane. With a gamepad however you can move your hands, arms more freely.

Along with that I am looking into chorded keyboard methods and eyetracking.

Please respond to the comment if you think this sounds interesting!