I can hook my app into the \"Share page\" feature using the following intent-filter:
But I would like to go a little further and limit the filter to intents with specific URLs in them, for example URL of a YouTube video.
What you are asking for makes no sense to me as written.
Perhaps you really mean:
But I would like to go a little further and limit the filter to ACTION_SEND requests where the body extra contains a specific URL
In which case, that is impossible, sorry.
Or, perhaps you really mean:
But I would like to go a little further and limit the filter to ACTION_SEND requests issued from random pieces of software that happen to be thinking of a specific URL at the time user happened to press "share", such as sharing the current YouTube video being played in the YouTube app
In which case, that is impossible, sorry.
If neither of those guesses really hit what you are asking for, please consider editing your question.