Feedify
I built another thing. Feedify will make Atom feeds out of things that don't have feeds, because I like having feeds. Basically, I got bored of having to jab at 5 icons on my phone every time I wanted to do a sweep of "what my friends are doing" - I'd much rather just subscribe to feeds and my RSS reader can tell me about things.
Right now it'll make feeds out of Flickr and Instagram photo uploads of your friends. These were easy - they map directly to single API calls to the respective services (in the case of flickr, this leads to unavoidable disadvantages with the feed. But that's life). As and when I think of more things that are easy, I'll add them.
So yes. Feedify. Play with it.