Well yes and no. The current prosthetics attach to the nerve endings in the hand/leg that normally regulate movement and use that to simulate it. They need a lot of training (even after years of use its still not easy) and are expensive. however if you are paralyzed or lost the nerves in an accident you do not have access to those nerves, so it would not work. However doing brainwave scans have been proven to be controllable to some extent.