Assistive technology is technology, or enhancements to technology, or methods of using technology, that makes it possible for disabled persons to use technology (or to use it easily) that they were formerly unable to use (or to use with only some difficulty). Moreover, according to the advocates of assistive technology, all too often, technology is created without regard to disabled people, and thus barriers to new technology-created opportunities are thrown up.
Universal (or broadened) accessibility means excellent usability, particularly for disabled people. But, argue advocates of assistive technology, universally accessible technology yield great rewards to the normal user; good accessible design is universal design, they say. The classic example of an assistive technology that has improved everyone's life is the "curb cuts" in the sidewalk at street crossings. While these curb cuts surely enable mobility impaired pedestrians to cross the street, they have also aided parents with carriages and strollers, shoppers with carts, travellers and workers with pull-type bags.
Consider an example of an assistive technology. The modern telephone is, except for the deaf, universally accessible. Combined with a visual feedback such as a calculator has, however, a deaf person can use a device like a telephone.
Deaf people don't have more trouble dialling than hearing people, so I'm not sure this is a good point. How about:
Combined with a text telephone (in the USA generally called a TTY) which converts typed characters into tones which may be sent over the telephone line, the deaf person is able to communicate immediately at a distance. Together with "relay" services (where an operator reads what the deaf person types and types what a hearing person says) the deaf person is then given access to eveyone's telephone, not just those of people who posess text telephones.
Another example: calculators are cheap, but a mobility-impaired person can have difficulty using them. Speech recognition software could recognize short commands and make use of calculators a little easier. People with mental disabilities would appreciate the simplicity; others would as well.