Personally I would design it so that it can be controlled by a single big toe - side to side motion controls orientation, up and down motion controls open and c

Personally I would design it so that it can be controlled by a single big toe - side to side motion controls orientation, up and down motion controls open and closed position. That way you can have one on each hand. Combine it with a load cell on the bottom of the shoe that activates and deactivates it based on how much force is applied so it's not wiggling around while you're walking. I'd also add some small vibrating motors that can be used for haptic feedback from the thumb so you know when it's touching something (by the vibrators being on) and even how much force is being applied (by the amplitude/frequency of the vibrations). Also not sure how I feel about the cable drive. Of course it does behave somewhat like muscle and allows the motors to be located some distance away, but I think for a thumb analog you need a certain level of precision control over position and force applied that a cable drive just can't give you. Like this is fine for grasping but you could never use it to type or fumble keys. I'd probably go with a bar linkage across the back.