Why don’t you put an option for see another apps or websites to play something like series or movies? Just asking, could be nice
Not sure if you still need an answer here, but just to say that you have access to (currently) 17 additional services, including vimeo and dailymotion. Just click the down arrow / icon to the left of the searchbar.
See here (scroll down to “Selecting Videos”): How to use Watch2gether?.