As my son’s carer and constant companion, I agree with this recent blog post from the great guys at Komodo Open Labs in Canada – (makers of the Tecla). In an ideal world, they conclude, the iPhone 6+ is the best choice of phone for a quadriplegic.
The only thing I would add to their reasons for nominating the iPhone 6+ is that I recently watched Christopher in a store, using his head switch to test-drive a 6+ in Landscape Mode. He was absolutely delighted, noting that he is currently limited when watching videos on his wheelchair-mounted iPhone 6, because he has no way to rotate the screen between landscape and portrait modes at will. With the 6+, he could have it mounted permanently in Landscape Mode.