Life Fitness, a division of Brunswick Corp., plans to offer seamless integration with Apple Inc.'s iPod players in upcoming products. The new fitness machines, equipped with liquid-crystal display touchscreens, will allow users to plug in iPods and headphones and peruse their song libraries or watch their videos on the console as they would on the portable player itself. This will recharge the gadget's battery at the same time. Life Fitness said it would make the first product available at the end of March. Your workout at the gym isn't going to be any less painful. But the world's leading commercial provider of exercise equipment might at least help make the session on a stair-climber or treadmill more entertaining.