Artifically constructed extension nerves!
New and interesting developments in the field of neuroprosthetics! Researchers at the University of Pennsylvania are culturing living data cables by stretching nerves! Because nerves do not mix well with nonorganic structures unless they are coated with organic compounds and practically grown there, the most ideal way of growing nerves is to take a section of viable nerve tissue, culture it in a growth medium, and slowly stretch the section of nerve. The idea is that the neurons are stretched away from one another, so the neuronal bodies and axons will lengthen to fill the space. Interestingly, nerves will stretch at the rate of one centimetre per day under ideal conditions; the longest cables so grown are 10cm in length. Extension nerves grown using this technique were used for conveying relatively simple impulses back in 2001 (!), and test-type extension nerves are already seeing medical use in repairing the peripheral nervous systems of human patients. I said the same thing you probably just did: "How the hell did I not know about this??"
However, bridging damaged nerves is one thing, but using the nerve cables to connect electronics to the nervous system is another thing entirely, and this hasn't yet been done with these cables. Animal tests are scheduled to begin soon.
I don't think that they'll have much trouble getting the artificial signals to the brains of test subjects: Professor Kevin Warwick of the University of Reading, England did just that a couple of years ago in his famous experiment in which he grafted a basic plug into his peripheral nervous system and used it to convey data from ultrasonic sensors and a computer into and out of his nervous system.