Are your Facebook friends or Twitter followers tired of your incessant posts about The Voice or Game of Thrones? Enter Zeebox, a new app available in the U.S. catered to the most avid TV watchers to keep the conversation going while a show is being aired.

Comcast, the largest U.S. cable company  and its entertainment unit, NBC Universal, are investing in a start-up called “Zeebox”, which makes an app meant to be a so-called “second screen” used by viewers while they are watching television.

The companies declined to provide financial details of Comcast’s stake. UK TV provider BSkyB invested a reported $15 million in the company in January. The free app has already gained some popularity in the UK, where it has 1.5 million users signed up.

More than 300 shows across 28 Comcast-owned networks will be represented on the Zeebox app, said NBC Universal’s Executive Vice President of Strategic Integration Page Thompson.
NBC already has apps designed to complement live TV shows such as an e-book based on the supernatural show “Grimm” and viewers using Zeebox will be able to find it easier, Thompson said.  NBC will also launch an ad campaign on TV and the Internet in October which will encourage viewers to weigh in on Zeebox while watching TV.

While it pulls from Twitter feeds and lets you connect with your Facebook friends, Zeebox also has its own messaging service and trending topics called “z-tags” that make it easy to track what TV viewers are talking about. ZeeBox sees advertising opportunities for z-tags on its service.