New Scientist is reporting that the busy personnel at MIT's Media Lab are at it again. They've developed a piece of software that listens to a small USB postal scale and translates various weights into functions. From the article: "Placing your mug on the scales might launch a web browser, for example." Presumably you'd have to leave your mug empty (or full), lest you invoke a new function with each successive swallow.
I'm not exactly opposed to external controls. I myself once developed a system for browsing movies that had physical controls (a few switches and knobs) and, at the risk of "tooting my own horn," I have to say that most people thought it was pretty stupid: taking your hands off the home keys so you can press PgDn is one thing; taking them off the keyboard altogether is another. And, yes, I know you have to abandon the keyboard in order to use a conventional mouse--which is why I use the little stick between my G and H keys. Typing is (I think I'm right about this) the highest-bandwidth channel from human to computer. (Exception: a piano played by a professional--but that's a very specialized input device for very specialized people.) There has to be a pretty good reason to give it up.
What we need are external controls that don't require your hands. These are common for people with various kinds of physical deficits--less so for others. I suggest we start with the humble office chair, which already costs $800--so augmenting it with sensors needn't materially increase its price. Examples: bouncing up and down in order to scroll--the faster the faster. Rocking forward to expand your view; rotating back and forth to move the insert point across a line. (And--whee!--once all the way 'round to shut your machine down on a Friday afternoon!) There are other possibilities: pedals (there are plenty of these: google "mouse pedals"); eye tracking (google "eye tracking mouse"); and Galvanic Skin Response (aka GSR: measures how much you perspire), in which you'd control a continuous function (like volume) by becoming more or less nervous. The possibilities are, alas, endless. Finally, there's one physical interface that's discussed only in hushed tones: (inadvertently) pouring Pepsi on your laptop invokes the "Get me a new machine" function.