TV enhancement startup Zeebox has just closed a deal with Viacom that brings a slew of new cable channels into its service, the startup announced today.

The Viacom partnership comes just days after Zeebox’s official launch in the U.S. under a partnership with Comcast/NBCUniversal and a handful of other popular TV channels, such as HBO and Cinemax.

Zeebox is a self-described “sidekick” for people watching television programs. The service, which is available via the web and mobile devices (aka the second screen), provides users with channel listings, information about shows while they play, content discovery, and various social features that let you interact with friends who are watching the same things. Media companies love the service because it provides yet another way for them to deliver ads and serves as a platform to sell products featured on TV shows.

Under terms of the deal, Viacom will back Zeebox with investments and promotional commitments, meaning many of the entertainment company’s top programs (South Park, The Daily Show, etc.) will get the Zeebox enhancement treatment.

This is a smart move for Viacom, whose cable channels have always had a strong following online.

Founded in 2011 by former EMI executive Ernesto Schmitt and former BBC iPlayer CTO Anthony Rose, Zeebox has offices in London and New York.