Phosphorous pixels, liquid crystal, LEDs, lasers, electronic ink and now little flames used as pixels of a display. It works by transmitting "sound waves through a flammable gas creating alternating high and low pressure zones."
They call it the Pyro Board and it's pretty neat. It's also the first display that can grill some burgers while playing your iTunes screensaver. And that alone makes this the best display technology ever invented. [Thanks Karl!]