The fact is there are many types of disabilities. There are movement disabilities, sensory disabilities, even simple learning disabilities.
These run the gamut, from quadriplegia to carpal tunnel syndrome on the movement side, from total to color blindness in the sensory area, and from autism to simple ADHD dyslexia in the learning area.
The amount of remediation you need, and the type of remediation you need, in order to happen will vary.
That's reflected here. My co-author, Martin Bayne, is nearly paralyzed by Parkinsonism. He is required to live in a nursing home, although he's just in his 50s, as I am. He requires enormous amounts of technology just to stay alive. I, on the other hand, require very little, although one of my children is dyslexic, and my wife complains of both arthritic pain and carpal tunnel.
Assistive technology, then, is in the eye of the beholder. Where you stand depends on where you sit. And thus defining it is simple. It's whatever you need in order to be productive.
What you need and what you want, of course, may be two different things. A quick example. A Gaurang Kanvinde brags that he has a great new technology for the blind called Accessible News. The software essentially strips ads out of news sites, and enlarges the actual copy for use by screen readers.
Is this necessary? No.
Does it assist blind people in accessing the news? Yes, somewhat, although there's also information in ads.
Is it a good thing? You decide.
And that's the important point. You decide what you need. You need to be in charge. And that's what we hope to do, empower you.