There's this really interesting arts installation happening concurrently in London and New York right now. The "story" of the telectroscope is that it is an unfinished project from the Victorian era, lost to time but now being completed. Both Gothamist and Londonist have written pieces on the exhibit. This project is being produced by a group called Artichoke, who have been doing stuff like this in the UK for a long time now.
I just love large scale interactive pieces like this. I adored the installation Pulse Front by Rafael Lozano-Hemmer at Harbourfront at last year's Luminato festival. (Press release quoted here.) Wish I could see this up close. Thanks to the internet, at least I now know it exists.