One stroke for any character on the standard 88 key keyboard.
The Evolution of Thumbscript
Beginnings as a keypad input system, 10 WPM
Faster and smaller as a pen-based PDA input system, 20 WPM
Feather Touch Input Device: Blind input for any device, 20 WPM.
Nano-Keyboard: Concept for a Bluetooth enabled input device that allows blind input with one hand.