Zinc is an iPhone app built for exactly this purpose. Because a native tvOS app is also included, I can bookmark content as it pops up on my radar, then sit back and watch later at my convenience on Apple TV. You can toggle watched/unwatched status, mark videos as favorites, or remove them; the iPhone app adds the ability to share with others.
There are two ways to bookmark videos: The built-in Safari extension, which can be used with any iPhone app that supports iOS 9 sharing, or an extension for the desktop version of Safari; there’s also a bookmarklet for Chrome or Firefox as well. Zinc doesn’t actually store this content, even for offline playback. It’s just a link, so if the video gets taken down later, you won’t be able to watch it.
Unfortunately, bookmarking is hit or miss: With more than a few websites, the Safari extension refused to work at all on iPhone, displaying an error. Zinc also failed with videos hosted on this very site (boo!) or when trying to add Twitter-hosted content, such as those popular Batman v Superman trailers.
Oddly for an app focused on saving content to watch later, there’s no way to resume from where you left off or manually bookmark videos already in progress. And although Zinc works just fine on iPad, there’s no native display support as yet.
Zinc shows promise, but the first release doesn’t quite live up to its ambitions of becoming a universal video bookmark service.