This is the TV-B-Gone—it is a single-purpose universal remote that is used to shut off a large variety of televisions. You can see a video of it in action. It’s open-source, so it’s fairly easy to build using the instructions included on Ladyada’s website.
I was thinking about combining that with the Turn-Signal Biking Jacket project we looked at last week. We could basically build this remote into the front pocket of a jacket and run a switch to the tip of the sleeve and the go around the mall and turn off all the TVs.
And on a different, but related note, check out this blog, Creative Physical Computing, many, many in-progress projects using things like Arduino, Max/MSP/Jitter, Processing, Quartz Composer, etc.