WhisperSystems/TextSecure — pull request #568 by b0m0x (2014-01-23 13:08:00+00:00)
Title: Spamfilter

This is a spam filter for TextSecure. Messages from filtered senders are marked as read when received and no notification is shown, but the message and thread will still exist and appear in the conversation list (but it is visually indicated that they are marked as spam). Senders can be added/removed from the list via the contextual action bar in the conversation list view.
I agree this could maybe use some refactoring / good looking icons / management activity, but that's only necessary if you are willing to merge this, I personally do not need it in my "private version" ;)
I think a feature like this is useful in general, so maybe you want to adopt the implementation or the concept.