bicep twist was probably the wrong term. I just want a joint that twists below the shoulder as in fact when the shoulder twists the skin aroud the shoulder hardly moves at all. The movement mostly occurs further down and this joint is for these purposes. I am not looking for any realistic deformations in terms of muscles.
if all the rotations come from the shoulder skin weighting becomes complecated and the extra joint would make things both simpler and more like actual movement, though that doesnt really exist.
check out www.cane-toad.com/tuteRig_Shoulder.htm
I find the wrist is not simply a ball joint. The twist in the wrist comes from the two forearm bones rotaing around each other which is more complex than a wrist ball joint. This is simplified in maya by adding a joint in the forearm which can be used for twisting of the wrist.