Assuming you have iOS 10.3 installed on your iPhone or iPad, and tvOS 10.2 on your Apple TV, the feature should be ready to take for a spin. A caveat, though: As 9to5Mac notes, those OS updates are only available in public beta and developer beta channels, respectively. Once those go wide, though, the feature itself should follow suit. This isn't a massive improvement, but hey, neither is a red iPhone 7.
iTunes movie rentals finally work across multiple devicesIt only took... oh, almost nine years.
Somehow, Apple went until 2017 before adding one of the most basic features to iTunes. You see, for the past nine years, when you'd rent a movie via the app, you'd have to watch it on the device the rental originated from. So, if you rented Manchester by the Sea on your commute, watched a few minutes and then wanted to finish bumming yourself out on your big screen at home, you were out of luck. With the latest version of iTunes (12.6) and "rent once, watch anywhere," that's changed.