Graffiti Research Lab, FAT Lab, and a number of likely affiliated technologists, artists, and graffiti writers are spending the week working on an eye-tracking system attached to a pair of plastic frame glasses to write graffiti with light. From what I gather, this would allow them to avoid using those super-powerful lasers.
Follow their adventures on the blog, or on their own twitter-esque microblogging tool, fucktwitter, based on the free software, Laconica.