LOS ANGELES (AP) - Comcast and subsidiary NBCUniversal are taking a stake in zeebox, the maker of a so-called "second screen" app that people can fiddle with on mobile devices while they watch TV.

The cable giant isn't saying how much it's putting into the company.

Executives say that starting next month, Comcast will start advertising how zeebox will be integrated into its shows.

The app gives users information about people and products that appear in shows, allows users to see what their Facebook friends are watching and points users to iTunes so they can buy songs that come up during shows like NBC's "The Voice."

The idea is that if viewers are more engaged with shows, they'll keep coming back. The second screen also gives TV networks another opportunity to raise advertising revenue.