If I had mod points, I'd vote this up, especially since it is actually relevant to answering the person's question.
Sorry I don't have any sources, but I know I've read a fair bit about experimental brain interfaces as Multiio describes, but from North American sources, so hopefully some usefull stuff turns up. As far as that goes, the wikipedia article on Brain-computer interfaces has some hopeful links.
Of particular note is all the succesfull experiments where they've had monkeys controlling robotic arms to feed themselves, using brain-wave monitoring devices to provide joystick type input into a computer, and stuff like that. From what I can tell, that's just the "proven and done" stuff. More complex things like outputting text directly to a computer makes sense to me, but I haven't seen any mention of that sort of thing.
To all those who, instead of answering the question have been providing "pull the plug" or "why don't you research ways to kill them" answers: don't assume anything less than perfect mobility is essential for an enjoyable life. I, for one, would want to keep on living so long as I can keep learning and experiencing things. Even if it amounts to never doing anything physical again and spending my time learning on the web, I still consider that to be a life worth living. We can't, and shouldn't, make these decisions for others, especially for those we don't know. After all, while there may be a few that really want to die and get a lot of media attention, there are just as many, probably more, who share my view: never pull the plug on me until my brain has completely, utterly, and without the slightest trace of a doubt ceased activity. And even then wait a week or two just to make sure it wasn't just faint for a bit before doing it.
Whenever locked in cases like this come up, I can't help but think of Anne McCaffrey's brain-ships series. Basic premise being that locked in people were hooked into spaceships. If they can control prosthetics, they can control anything else, the theory goes. If they can never live outside a machine, well, give them the best possible opportunity to be as productive as possible in a machine, ideally by doing things that un-injured people can't do. I'm sure it is possible, but it is a field that needs a lot more work.