What about an app that lets you gauge the mood on twitter? By judging the tone/mood/content of posts you could determine the state of the community. Imagine be

What about an app that lets you gauge the mood on twitter? By judging the tone/mood/content of posts you could determine the state of the community. Imagine being able to type in a keyword say: chess and getting a twitter consensus or summary of the community's opinion on this topic. Maybe something like this already lives? I know FBook already has something like this.