I’ve been paying a lot of attention to chordic keyboards. These are typically one handed and portable, these devices let you press button combinatins to express which character you are typing. Most of the attention chordic keyboards get is based on their utility for wearable/portable computers and their ergonomic advantages.
So far, I haven’t seen any chordic keyboards with PDA drivers and that is a shame because I’d love to try one in that setting.
One to keep an eye on is my favorite, John McKown’s Chordite – http://www.chordite.com and check out the movies at http://www.chordite.com/moviepage.html. John retains the rights to sell these devices commercially, but all of his specs and construction tips are available on line for you to build your own. PS2 and USB(using an adapter).
A mechanical engineer just started looking at John’s prototypes and build descriptions/tips. His impressions are here.
A year ago, I built one of these(as did Gordon and Craig), but we never mounted the switches on anything close to ergonomic. I’m hoping that the solution to the fully adjustable, lightweight chordite unit will be made possible by some soon-to-be-discovered kids building toy(legos, technic, erector, k’nex, etc).