Most articulated robots simply model this motion using the wrist (most often Axis 4, on most typical 6-axis robots).
That's a lot of torque to fit into a package that can fit inside a humanoid. Not to mention you haven't touched on your power supply and driver capacity. I mean, you could easily end up with a servo the size of a bowling ball that requires 3-phase 480VAC and an industrial-grade driver the size of a toolbox (not to mention industrial-grade pricing). There's also the speed/torque curve to be considered. My first thought is that you'd want to look into servos like the Dynamixel series, run through a gearing chain to increase torque.
