Last Saturday, during a conversation with Santiago he showed me dasher running on his Linux laptop (Here's an article on it from The Economist).

It is amazing. At first it is relatively weird to use, but that feeling goes away quite quickly. And then you start "typing" away without problems (I haven't tried adding a training file to it though, the basic package worked well enough for simple testing). But you won't really know until you try it. Go check it out--they have binaries for most platforms.

If this isn't squarely part of the future of typing on mobile and input-restricted devices (aside from Speech/Handwriting recognition and gestures), then I don't know what is.