And the best part isn't even that it uses 10,000 iPhones.
It's that they apparently use the Near Field Communications feature to effectively talk to one another, which creates the lighting effect and the finale that you see in the video above, by AatmaStudio.
Edit: Scratch that, it's likely just CG. Boo.
10,000 iPhone 5 Domino [YouTube via Laughing Squid]