Marco Tempest] has developed some software called MultiVid that allows synchronized video across multiple iPhone or iPod Touch devices. For this to work, all of the devices must be connected to the same WiFi network. Playback can be controlled from any one of the iPhones/iPod Touches or from the Mac running the controller software. There is of course the option of connecting to larger monitors through a video output cable. The app also supports OSC. We’ve embedded the example video as well as a video detailing the software setup after the break.
The client software is available at the apps store and controller software can be downloaded from [Marco's] website. Both are free which is our favorite price point.