I just noticed this in the October issue of the IEEE Spectrum: New Brain-Machine Interface Reactivates Monkey's Paralyzed Muscles.
This is very encouraging news on a number of fronts. Of course it is good news for spinal trauma patients and patients suffering from degenerative structural nervous system disorders. But it also potentially bodes well for some unusual types human-computer interfaces.
Picture the scenario described above, but with the downstream actuator side of the circuit embedded in the body of someone other than the person whose brain is generating the signal. Imagine a surgeon teaching a surgical resident a very tricky procedure, and able to guide the resident's hand just as she would her own. Although the stimuli are coming from the outside, I'd bet that the resident's nervous system would retain the "muscle memory" of the surgeon-guided actions, aiding the buildup of tacit knowledge that characterizes expertise.
That's the first outside-the-box use that's occurred to me in a few minutes of reading and thought, but this is outside my current scope of activity (darn it!). I'll bet many other and better ideas will arise in the fertile minds of the biomedical engineering community as this unfolds.