As part of its effort to launch the new Prius iPhone app, which is available for free on iTunes, Saatchi & Saatchi L.A. conceived this stunt that allows people to draw on the Reuters billboard in Times Square. The event runs through today and the billboard can be viewed on a live webcam on the Reuters site.

The app itself allows users to tour the new Prius, interact with the car's ads like the billboard and basically, have some fun, with a sketching feature and a multi-level game using the iPhone's accelerometer.