I've mentioned before that I worked for a couple of years providing computer support to disabled college students, faculty and staff. While much of what I worked with was otherwise standard gear tweaked slightly to accommodate special needs, one of the coolest pieces of tech I ran across was a note recorder for the blind. The user didn't just talk into it, he typed notes to himself using an eight-key chording keyboard; the notes would then read back to him in a computer-generated voice.
Well, that was the early 1990s. Today, the blind have a new note-taking device: the BrailleNote PK. It does everything the earlier version did (including speech output), but also has an 18-cell Braille display (essentially a series of pins that form Braille characters, read by running fingers along them), USB & Bluetooth for syncing with a PC, WiFi and a web browser, and a media player (along with a bunch of other features) -- and it weighs just under a pound.
It's been my experience that technologies and adaptations intended initially for the disabled very often evolve into technologies for everyone. Sometimes, however, the reverse is also true: technologies meant for the mainstream can, occasionally, be adapted and transformed so as to accommodate those who can otherwise be cut off. And that's pretty cool.
Interesting that you should mention that, Jamais! I agree completely.
Assistive technology has been building steadily for a long time, with a major boost in the late Seventies from desktop computers, but it has really exploded in the Ninties with the emergance of many factors. OCR, GPS, robot legs, handwriting recognition, speech recognition and even language translation are steadily improving and growing cheaper.
The BrailleNote PK is a market leader among notetakers (The jargon for blind accessible PDAs.) but many of the newer ones now contain GPS cards as well. This gives people with visual difficulties the independence to navigate a huge street plan with more reliability than a veteran cab driver.
But as you well point out, there are lot of unexpected benefits from improvements in assistive technologies. For example, did you know the arrival bells used with elevators were originally put there for the blind? Now we all use them without thought to the added convenience. We don't have to face the elevator to know that it has arrived--just turn to the bell.
I've learned these things over the last eight years working as a freelance webmaster and accessible web design consultant for six companies that build and sell assistive technology. It is an interesting field seen from close up! And I agree that it's "worldchanging."