I look at the artificial kidney that I talked about in my last post as a sort-of futuristic automaton. It can work (in principle) on the body's internal power (the blood pressure) and does not require the frequent tweaks (again, in principle) that are required with conventional dialysis; thus giving patients more freedom with their lives.
However, the technology that really has the trans-humanist in me jumping up and down with excitement is the promise of regenerating a "natural" human kidney in the lab. In Greek mythology, Prometheus' liver would regenerate even after an eagle nibbled on it every day, all while the poor fellow lay chained to a rock (he was lucky the eagle didn't mess with his kidneys, which don't quite possess the same regenerative capacity!). My fantasy is not quite the same, but what I had always conceptualized is that with the advances in regenerative medicine, we might be able to just play God, and "make a kidney", a real human kidney, not a chimera of materials from man and machine. It always seemed to be the stuff of science fiction.