The more details you can give us, the more specific information and higher quality responses we can give you.
Are you interested in a
4-bar linkage? (Or even an
8-bar linkage).
Are you looking at
telescoping arms? How about a
pneumatic telescope? Or even powering your extension with
surgical tubing?
Would it be powered at the
shoulder joint? Or would it be powered from the base by
lead screw or
winch? What about any
counter-balacning?
And there are tons of more factors that can apply, and we haven't even reached the actual end-effector yet! Like I said, more info you give us, more we can help.