BEIJING -- High-tech televisual bells and whistles have carried couch-based Olympic watching way beyond the mere reality of being here. Thousands of cameras are catching the action in China -- every one of them high-definition. Yet for a feat of engineering magic that dazzles as it baffles, nothing beats the DiveCam.

On TV, a diver walks out onto a platform. The camera fixes on him. He waits. He leaps. And then -- somehow -- the camera stays with him as he plunges. In the instant it takes him to break the water's surface,...