Boxfish captures all closed-captioning information, indexes it, then makes that data searchable in a Twitter-style interface. All in real-time.
If this technique sounds familiar, perhaps it’s because Google did something very similar way back in 2005:
The service, Google Video beta, searches closed caption information that comes with programmes. It only searches US channel content currently.
Results list programmes with still images and text from the point where the search phrase was spoken.