My best friend in college told me about a keyboard that allowed you to type with only one hand by remapping both halves of the keyboard to the other side (swapping when a toggle key is held down), so that it had a backwards QWERTY layout. So, essentially, you could reach the whole keyboard with either the right or left hand.
It will soon be expanded to instead remap keys based upon a configurable ini file so it could be used for other purposes.