Well, we've already got good working prototypes of artificial muscles...

It's only a $100 toy--an aquarium of swimming robotic fish developed by the Eamex Corporation in Osaka, Japan. What makes it remarkable is that the brightly colored plastic fish propelling themselves through the water in a fair imitation of life do not contain mechanical parts: no motors, no drive shafts, no gears, not even a battery. Instead the fish swim because their plastic innards flex back and forth, seemingly of their own volition. They are the first commercial products based on a new generation of improved electroactive polymers (EAPs), plastics that move in response to electricity.

and artificial skin...

Electrical engineers Sigurd Wagner and Stephanie Lacour at Princeton University have developed a kind of connector incorporating broad metal strips that, unlike wires, can stretch up to twice their length and still conduct electricity. They think it will be ideal for use in robot skin.

The hardest part, of course, is the brain.

We're still working on that.