Perfect for disabled people and mobile worker, the one-handed FrogPad Mobile boosts only 20 keys and is 1/5th the size of a normal QWERTY. So far you could hook it up to any mobile device only with a USB connection but FrogPad has been recently Bluetooth-enabled.
![frogusb-thumb[1].jpg](http://www.we-make-money-not-art.com/frogusb-thumb%5B1%5D.jpg)
Check also pcmag for other keyboards.