The Switch (1993)

Larry McAfee is paralyzed from the neck down following a motorcycle accident. He gradually loses the will to live, in the meantime befriending a talk radio DJ (portrayed by Craig T Nelson) over the phone. The two meet each other and become friends, though Larry still wishes to end his life. The DJ reluctantly has a switch installed on Larry's life support that Larry can activate at any time (via his mouth) to end his life.