I think it would be neat to download and store what you had already seen, as well as bringing something like Friend's subjects, and how many comments they have.
I don't see anything like this in the protocol docs, however. I see Checkfriends, but what I'm reading only will show me IF something has changed, not what has. Is there anything in the protocol docs that anyone can think of where I could see what has specifically changed for the entries of a Friend of my user?
Now that I've typed this, it sounds incredibly more confusing.