A new feature for owners of the fourth-gen Apple TV called Live Tune-In has started getting a heavy push on the splash screen today. Live Tune-In," a feature letting people jump straight into the live TV feeds of select apps. While a lot of the device's offerings are games, music and on-demand video, even in the 21st century sometimes people just want to flip channels and see what's on.
It should be a universal feature but it's not with only some apps having access to the live tv feature. The feature is triggered by a SIRI command, examples given included "Watch CBS" and "Watch ESPN live". As seems to be the case with so many of Apple's offerings, Live Tune-In will not do a thing for Discovery since a user has to be subscribed to a service with a live stream before it becomes searchable.
How you discover when a new and noteworthy show is on is still another thing altogether and personally I'd like some sort of notification service baked into the Apple TV to remind me when Gotham is on, or comes onto netflix rather than relying on a third party app.