Obviously, no such technology exists at the moment. But brain/machine interfacing has been proven to work in certain situation: scientific experiments have demonstrated that looking a monkey's brain up to a signal-reading machine can allow the animal to control a robotic arm in order to feed itself as if the robotic arm were part of its own body.
The technology has been (understandably) focused thus far on people who are quadriplegic or otherwise paralyzed, but one day, it might actually be applicable to gaming. Imagine standing on a mountain in Skyrim and actually feeling the wind on your face - with no controllers in sight! Unsurprisingly, however, there are a few bumps in the road to address before we get to this point. Check out the video above from Gamespot for a full explanation.