actually they already have this type of printer where it can literally print 3d objects, I believe they did it once on CSI:NY for the first or second season...and scientist have actually created (and are still developing) heart valves that were printed using a special kind of printer, I remember seeing that on Discovery Channel some time ago.
Yeah, these do exist outside of television. I don't remember the exact details, but I believe they work by laying down layers of plaster and glue just like a regular printer. Just with lots more layers. They're mostly used for indutrial applications.
Edit: Damn it, Jafo. Here, have this link anyways. http://en.wikipedia.org/wiki/3D_printing
