At last the prosthetic arm is alive (to some degree). Modelling the arm wasn't as hard as I thought it was going to be. There are a few issues with the fingers I admit, but other than being told what polygons to use and building it up from there, I don't think it's half bad (I'm sure someone will disagree though). Here are some pictures of the arm including wireframe, normal view and then smoothed.
In terms of texture I was think of making the arm look like it was made of plastic, probably in a flesh colour to make it a bit more unsettling.