Half QWERTY One-Handed Keyboard
Half Qwerty uses the skills that have been acquired after many years of typing with two hands. Half Qwerty allows the remaining strong hand to do what it has always been trained to do, on the side of the keyboard on which it has always typed..
Each of those keys on that side does double duty. They type the key they would normally type, then, when one of the keys on the opposite side is needed, the user holds down the space key, and key does the other letters from the other side of the keyboard.
More information: http://www.onehandedkeyboard.com/halfqwerty.html