I have an EASY one for you.
I've now got to put in a "block user" function in my bbpress app to comply with Apple's regulations on user generated content. Sigh. Quite a learning experience dealing with Apple. That said, I think it is a very good feature to have.
If I could get the user ID anytime a topic list or topic/reply is shown, then I could store the blocked user ID locally in the app and not show the content if the blocked id matches.