It's either a triumph of hacking, or some pretty decent video editing. Either way, this video purporting to demonstrate the takeover of a number of video screens (including a rather famous one in New York) using only a transmitter and an iPhone is worth checking out. Watch and decide for yourself before we render our judgment:
...the way it works is pretty simple: plug in my transmitter into the iphone 4 and play back any video clip. you can play it through the ipod feature or through the camera roll. the transmitter instantly sends the video signal to the video repeater and the video repeater overrides any video screen that it's being held next to. it doesn't matter what shape or size the hacked screen is because the hack video will simply keep its correct dimensions and the rest of the hacked space will stay black.
Seems basic enough, until you consider that the headphone jack being used can't handle transmitting video, and if it could, Apple would have held a press conference to tell us about it. Therefore, we call hoax. Maybe we're missing something on the technical side, but one thing is for sure--these guys get an "A" for knowing what makes a good viral video.