VoxForge
Dasher, is a mouse interface that allows you to enter text without a keyboard:
Dasher is a text-entry system in which a language model plays an integral role, and it's driven by continuous gestures. Users can achieve single-finger writing speeds of 35 words per minute and hands-free writing speeds of 25 words per minute.
Demo video located here: Single-finger text input
I have actually used Dasher 'in production use' when I was having some (temporary) problems with my throat. It's a great approach and very good software. I think it does need some minor improvements, but I'm not entirely sure since I do not use it every day, and so might have missed handy features.
What might be very interesting about the Dasher approach is that they already have very good 'language models' for spelling purposes based on about 2 MB of text for many languages of the world. It might be interesting to consult the people from Dasher when spelling features are built into e.g. Simon, or gnome-voice-control.
There is also a version of Dasher that works in symbiosis with speech recognition. If I understood correctly, you start with some utterances, and then you use the Dasher type of control to choose between most likely interpretations. Might also be very interesting in the future, especially since open source speech recognition might not be as good as commercial speech recognition for a while. Therefore we might need a smart additional correction phase. Of course I might be completely wrong, because I did not have time to actually try this version.