"Speakers Corner takes a live feed from their website or your mobile phone and feeds it directly to the public display in the centre of Huddersfield, UK."

"hellomrpresident made it possible for you to send a message to Davos for the duration of the World Economic Forum's annual conference (January 25-29).

"A laser projector beamed messages onto the mountain side overlooking Davos, so that it can be seen by the hundreds of journalists and thousands of politicians and business leaders attending the conference."

Related to that, the Hellowworld project: "Send in your message, and see how it is projected by a laserbeam onto a mountain overlooking Ipanema Beach in Rio de Janeiro, onto the UN building in New York City, onto the most prominent building in downtown Mumbai or onto a 140 metre tall water fountain in Geneva. SAY IT NOW!"

"SimpleTEXT is a collaborative audio/visual public performance that relies on audience participation through input from mobile devices such as phones, PDAs or laptops. SimpleTEXT focuses on dynamic input from participants as essential to the overall output. The performance creates a dialogue between participants who submit messages which control the audiovisual output of the installation. These messages are first parsed according to a code that dictates how the music is created, and then rhythmically drive a speech synthesizer and a picture synthesizer in order to create a compelling, collaborative audiovisual performance. SimpleTEXT was originally funded by a commission from Low-Fi, an new media arts organization based in the UK."

Thanks to Carlos Gomes De Llarena for the links.