This is how Wikipedia defines accessibility:
For me personally, accessibility has two aspects - a human and a social side, and a technological one. The human aspect I will discuss on my site, which is focused on green politics. Here I often will discuss the geeky side of the assistive technologies. For many fellow developers and engineers accessibility compliance is just a checkbox that must be checked in order to get a government contract or just to "look good". For me assistive technologies are providing enormous fun by pushing the boundaries of technological innovation. They allow us to view the surrounding world in a completely different way by turning off some of our sensory or motor abilities and compensating this loss by reinforcing or enhancing other sensory abilities or inventing mechanical support tools. Quite often this way of thinking not only helps us to make our product accessible, but leads to general design improvements and completely new concepts. As an example, years ago when I was working on an astronomical project, my efforts to try to make an astronomical image accessible with VoiceOver lead to a completely new control element that helped sighted astronomers quickly to find objects of interest.
Nowadays, I am pushing all products of my company to be accessible. It is still a long and difficult road to walk, but most still remaining obstacles are related to external production factors (e.g. it is almost impossible to find a package label printing shop, that also prints the labels in braille).
Finally, it is my goal to develop products that are specifically targeted for the accessibility sector. An example for such a product is the planned KenColour iOS application to help visually impaired to see colours. (To support this development we have also started a Kickstarter project.) Further goals are to develop apps to help health specialists and volunteers to improve eye-care work in third world countries, or transit and navigation software for the blind and wheelchair users. A book on Assistive Mobile Technologies is also on the horizon.