Most of us use a standard keyboard and mouse on our computer. Bill O’Brien has done an excellent job of cataloguing alternative input devices of many different varieties. If your wrist hurts, and you’ve got some bucks to spend, check it out.
Some input devices aren’t easily categorized — like the touch screen. IBM tried to introduce a touch-screen system about two decades ago. It was a clunky and unreliable. Sometimes you got what you touched, sometimes you didn’t, and sometimes you had to reboot the system. Hardly ready for prime time. Today they’re much more accurate and much better protected against moisture, dust, and the general grime and oil that collects on our fingertips.
Touch-screens also don’t need to be complete monitors. There are touch-screen overlays available for existing displays and notebooks. Of course, you’ll still need mouse-driven application software to interpret the screen touching. (In case you hadn’t noticed, your PDA uses a touch screen, as do many smart phones.)