Mood of USA from Twitter

We as a group had an idea to do mood mining on a Social Network Like twitter and fourSquare. And had came up with the name MoodEarth for our project candidate. However during our research we find something similar to what we had in our minds it is basicly using Twitter API to retrieve text along with location information and visualize the data. I can't say it is a tastefull work but still it is very close to our idea.