I think Backtype has already one...but this is interesting to see how it evolves. I know uberVU and Disqus partnered and powers now the conversation tracking on Mashable. Let's see what Artiklz.com will respond (another competitor)...

Yes, our API is live and documented here: http://www.backtype.com/developers/comments-connect

Also here's a great app that was built by a user of our API: http://convotrack.com/I1