Closed captions or subtitles are now applied to enormous numbers of media productions (due partly to legislation which makes it illegal to discriminate against hearing-impaired people).
Companies can even now pay to obtain a real-time profile of the frequency with which their corporate titles are used eg in global news broadcasts.
Today’s invention is an entertainment-related variant on this, to allow better access to a higher fraction of interesting stuff.
A channel hopping viewer could pay to enter a small set of (weighted, personal) keywords online.
When these appeared in the captions for anything on tv or the web, a short burst of that programme or video would play on their screen.
This would enable a new form of media consumption, somewhere between browsing and channel hopping, with the power to choose to stay with anything interesting that appeared.
Naturally, dialogue in adverts would be tailored in attempts to achieve even better targetting via this process.