Movie rentals on iTunes have finally received a key feature: the ability to watch them on multiple devices. For nine years, Apple has been forcing customers to watch their rented movies on whichever device the rental originated from.
That requirement is no longer in existence. iTunes version 12.6 allows users to “rent once, watch anywhere.”
The feature will work across platforms as long as you have iOS 10.3 on your iOS devices and tvOS 10.2 on your Apple TV. Those are still in public beta and should be fully available soon.