I first was introduced to Janet Echelman's public art installations on a visit to the Autodesk Gallery this past summer. Janet Echelman and Aaron Koblin's latest interactive installation is located in Vancouver, Canada. It allows visitors to create colors and ripples of light across the surface of the 300-foot textile sculpture. Visitors use their mobile phones to connect to the project's server and uses websockets to stream directly into Google Chrome. It takes all the collected data and spits it out to another Chrome instance which renders the graphics on the installation in real time. Basically, the installation is one huge, suspended web browser. See more about this on the Google blog.
A few weeks ago, I visited the Murmur wall at the Yerba Buena Center for the Arts; another interactive installation driven by public data. However, in this installation, visitors use their mobile phones to send 'whispers' (text messages) that are in turn displayed on LED screens.