Alexander Graham Bell
Bell's father, grandfather, and brother had all been associated with work on elocution and speech, and both his mother and wife were deaf. This influenced his life work. His research on hearing and speech further led him to experiment with hearing devices which eventually resulted in Bell being awarded the first patent for the telephone in 1876.
Why is it useful?
The invention of the telephone allows you to connect with people all over the world. Anyone can use it!