Software Application for physically disabled persons!

A random idea, which sparked my thought, is any application exists, which is a boon for persons with disability. Let a person has lost his/her limbs in any unfortunate incident and he/she posses adequate skills to do a job. This application inputs the voice and transfer the command into some event through which he/she can operate an application. It is possible? I feel very bad, while writing exam papers, these disable friends have to take a help of a writer to write the paper. Can our system have some means to help them?

Let me know If we can do something with this idea. Thanks