Stremio is pretty versatile. At its core it's like trakt. Let's you catalogue your movies and tv shows, track what you've watched, sync it between devices. It has plugins for playing them, ranging from commercial stuff (Netflix, Hulu etc), to torrents and even archive.org.

It's a versatile tool for finding anything to stream, regardless of source or legality. It also has a plug-in system so it is extensible to get the features you want. There's a watch party plugin even.