This is one of the best interfaces I’ve ever used. It allows you to quickly type with a keyboard (it’s an accessibility application, but can be used for other things, too). I found I was able to type about 3/5 the speed of a normal keyboard, with fewer mistakes.
http://www.inference.phy.cam.ac.uk/dasher/
It’s pretty much impossible to explain, so you have to try it yourself. 
