I have found the Condor soaring simulator to be a great way to test
PDA software. I find it far more effective than the demo modes most
software has. It comes very close to the real thing. You can simulate
all kinds of situations and actually test how the PDA reacts. It also
has the advantage of having to concentrate on flying the simulator as
well as working with the PDA - just like in real life. This shows bad
usability far more quickly than pure demo modes.