uh-oh ... Dr Curt Connors has been working on that for a while, but results have been less than heartening ...
I have my doubts this will ever work with mammals like us. If there wasn't something fundamental standing in the way, I don't think nature would have lost us the ability to regenrate limbs as we moved on from being reptiles to birds to mammals. In my evolutionist mind, of course. I don't so much doubt that you could grow an arm and transplant that for cosmetic use, I doubt you could make it work as a limb (like typing something or playing bass for that matter).