There is a type of keyboard that I find would be easy for some people with a movement impairment disorder. This is a one-handed keyboard for either left or right-handed users. These keyboards are smaller and are mostly in a square-like shape. The keys have two letters per key and a function to switch between letters. This may seem more difficult than a normal keyboard but can be very efficient once used it.
Some people with impaired mobility may find using a normal mouse hard.There are probably a lot of types of different mice out there for assistive technology. One of these mice is a joystick that mimics the mouse movements. You tilt the joystick to the direction you want the curser to be. The buttons are strategically placed so the user can easily use them.
These are only some of the assistive technology devices out there. I find a lot of these types of these on http://www.enablemart.com/. This site has a lot of different types of assistive technology including blindness, hearing loss, alternative input and more. All of these devices can come in great use. If you need or are interested in assistive technology you check out this site or Google for more devices.