A famous bearer of this name is Amyas Godfrey, a child actor on the Classic Nickelodeon show "You Can't Do That On Television". The name on the show was pronounced "Amy-us".
In Agatha Christie's "Five Little Pigs" (a Hercule Poirot mystery), the victim's name is Amyas Crale. The television show "Poirot" used the story (and character names) for one episode.
I have heard the name pronounced as Amy-us [/eɪ/mjəs]