Motion Analysis' Eagle Digital System was used for the facial motion capture in Peter Jackson's movie, "King Kong".
Andy Sirkus describes the process:
"I had 132 facial markers, and it tracks all your eye movements, so all the eye movements you see for Kong are exactly what I did. It's like wearing a digital mask, and it's all enhanced by the animators, of course. It goes without saying that the look of Kong and the whole way he's manifested in CG is a visual effects thing, but I'm talking about the performance and the acting choices that you see, the expressions, the emotion, everything that you see."