Quest64, also uses pie menus, although they all only have 4 choices, and its not a mouse interface. N64 game, not particularly great for its genre, but wasn't too bad either.

For Hawking's voice simulator, he can compose sentances and paragraphs and keep them in "ram" to say later. To compose sentances, words are broken up into catagories (and I assume, subcatagories) and he searches through them, then selects the word. If the word isn't listed, he can select letters to form it. I believe his composition speed was comparable to a slow typiest, which while much slower than speech, is pretty good.