Control systems for wheelchairs have to accommodate a wide variety of disabilities and capabilities; some people can use a joystick, others are restricted to blowing in a tube in different ways to signify left, right, accelerate, and so on. But one part of the body that is almost always fully intact and functioning is the tongue. Because motor control of the tongue is done through cranial and not spinal nerves, even the most high-up spinal damage survivable won’t affect control. So it’s the subject of much research as to how to best take advantage of the organ.
There are some control systems already on the market that use the tongue, and the military is researching using it as a “sixth sense” for pilots. The newest system for tongue-based navigation uses an implanted magnet, the position of which serves as essentially an analog control for movement, orientation and so on. It’s still at a very early stage, but it sounds like a promising technology and is already attracting grants. I was going to make some inappropriate tongue-related jokes here at the end, but I don’t have the heart.