An anonymous reader writes "Doug Engelbart should be known to everyone on Slashdot — he did invent the mouse after all, among many other inventions all of us rely on today. There was one more obscure device he came up with that never really took off, though. It was called the Chorded Keyboard, and consisted of a system that allowed you to type using just one hand. The key to this system was finger combinations, which allowed up to 32 different characters — more than enough for the alphabet. Now that one-handed keyboard has been ported to work with touchscreens, and it could end up being quite popular. The key benefit is the fact you can type anywhere on the screen and don't even need to see where you are typing. The only difficulty is learning all the key combos, but once you have them cold you may be able to type faster than with two hands on your smartphone or tablet."
Bonus: being software-only and open-source, it's much cheaper than a Twiddler