Using eye movement to type.?

Would like to find supplier of technology and equipment that would allow a person who has lost use of all movement barring eyes and the ability to move his head slightly form side to side. If what I heard is right he would be able to communicate by using his eyes focusing on a screen to pick out letters that then appear as a typed message. At present he is imprisoned in his own body and his only communication one blink for yes and two for no. Hoping someone can help. Lee