The brain does not have "areas" of processing. There is no "voice area" or "hearing area" or whatnot - there is no set place for these processes to hapen in the brain.
Recently my coworkers and I have been watching TED talks while completing our routine tasks, and I stumbled across this one. It deals with sensory input and the possiblity of expanding our senses. With very little understanding of the brain and nervous system, I'm going to make the assumption that the neurons in the spinal cord and in the limbs and whatnot are functionally identical to those in the brain. Therefore the idea that our limbs and other parts of the nervous system are just as involved with the process of learning as the brain itself. We must not view the brain and the nervous system separately, but as a single entity - as one organ all together. It is infinitely adaptable as all parts of it are essentially the same at the cellular level.
Now, this part is purely speculation on my end, but I believe that our brains are actually terrible at generating communications, and I would go so far as to say that it would be almost impossible to generate any form of communication without some form of input to gauge if what was generated has a positive or negative impact on the self.
Let us take a deaf person, for example. They cannot hear anyone's voices or various noises, or even their own voice, but they can sense them elsewhere. Another's voice can be read by reading lips, a loud noise's vibrations can be felt in the body, and their own voice reverberates in the head and can be heard that way.
This funcitons the same way with hearing people. As infants, we attempt to mimic noises of our elders and our brains will determine if the response is positive or negative from them. If it's positive, then the connections that are formed will grow stronger, if negative, then they will fade over time (no connection that is made can truly be unmade, just overwritten).
So, if we assume that all parts of the nervous system are functionally identical, and that we require some form of input to ensure that our output is met with a positive response, and the brain doesn't care where the input comes from, then all that would be needed is a sensor to hook up to some form of information source, any kind of device that can transform that information to a bodily input - in the video, Eagleman uses a vest with vibritory motors, other research has used electrodes or tactical feedback - and then hook that input up to the body.
I personally can imagine a square of electrodes on a patch no bigger than a keyboard key that is stuck somewhere on the body (perhaps behind the ear or in the armpit) this shocks the skin in some pattern according to an input, I would say an infrared or ultraviolet camera on the forehead, or radio antenna, maybe even sensors on another person.
Once the interface has been established, the possibilities are truly endless, and I would like to propose that we do not need to stop at simply adding sensing that provide input, but inputs that can generate outputs. With both understandable inputs and controllable outputs, we could effectively add more interfaces to the human body.
I would say that, given the above is mostly true (on a high level), then this technology exists already, all it needs is a reason.
I think the realistic future would consist of genetically engineering us to have slightly larger heads (still within the realms of normality, not talking about alien sized heads), and to possibly improve the efficiency of neural connections (that's speculative), and then adding these external and non-invasive interfaces to expand not only our worldy experiences, but our intelligence and capability of understanding it as well.