Nintendo wants to turn a movement that is a key part of its Wii video-game console into an exercise program with a new Wii Fit product. Announced earlier this week at the Game Developers Conference in San Francisco and launching in mid-May, the Wii Fit will use the motion-sensing controller and a new interactive Balance Board to create a workout. The board senses weight and motion, and the company said third-party publishers are also working on applications. Wii Fit is expected to retail for less than $100. Wii Fit is already available in Japan, and has sold over1.4 million units.