Comcast and Roku are launching a new Xfinity TV app, but it will only be available to Comcast users who subscribe to TV and broadband, and who have at least one set-top box provided by Comcast. "Rather than being a set-top box replacement, it’s basically another way you can log in to your existing Comcast cable account and view content, just like the website or mobile device apps," Consumerist reports.