Robotic arms have found their way into commonplace recently as a tool for people who have had to have their arm amputated. These robotic limbs have had to be controlled manually by their other functioning arm.
A new study announced, at the American Association of the Advancement of Science, that they have successfully produced an arm that they linked, electronically, to a monkey's brain. The monkey was then able to perform functions with the arm using his brain as the controller. According to this MSNBC article, the monkey was able to feed himself with the arm that is attached to his motor cortex. Andrew Schwartz, of the University of Pittsburgh is quoted as saying that it is not crucial that the 96 hair-like electrodes, connected to the brain, be placed exactly because the brain will rearrange its structure to get things done.
If they have done this with arms, perhaps legs are not too far behind.
Additional Article: Embracing the Artificial Limb - Wired.com