Under all the stuff shown at the CES 2005 the demo of the D-Box motion chair was the best.

In a little Cinema the company had about a dozen recliner chairs available. The D-Box Odyssee motion system simulates the motion in sync. with the action on screen. They showed a short segment of the latest Harry Potter movie. It was the scene when they sit in the train and the prisoner shows up. D-Box also showed a short segment of driving a formula one car. The motion of the recliner really adds to the experience similar to those virtual reality rides found in entertainment centers.
D-Box creates the motion cue CDs for most of the new DVD movies that come on the market. Those CDs have to placed in the control system and they play in sync. with the movie DVD.
It sure looks a bit funny to see such a chair in a living room infront of a TV and it moves and wiggles. Depending on the options a D-Box motion chair is around $5,000.
More details on D-Box.