Before there was Twitter, there was the Bio Mapping project by Christian Nold. Participants were equipped with biometric sensors measuring their stress levels via galvanic skin response and asked to wander around the Mission District of San Francisco, annotating their feelings and experiences in real-time, in an effort to map physical responses to geographic locations around the city. Think of it as micro-blogging with automatic emoticon detection.
Maps of other cities are available here, here, here, and here.
(Right-click or select the carrot in the upper-right corner to zoom in.)