Great idea; I've heard it a few times. I actually built this against an undocumented API call; if you watch the network tab when you open up GitHub, it makes an ajax request for JSON. I replicated that request with https.get on the server, then dump that json out on the page (to get around CORS problems.)
I think they're using sessions to determine if you're logged in / authenticated; so I'd need to either see if I can just pass in an oauth token and see what happens, wait for them to build an API around it, or just do the work of combing the repositories and build the data manually.
I would love to be able to authorize it with my Github account so it can read my contributions to my private repository. All around great work.