Video-out accessories: The iPhone 4 appears to use video-output circuitry similar to that of the iPad. Which means that as long as you have a recent, Apple-certified video accessory—for example, Apple’s Composite AV or Component AV cables, Apple’s iPad Dock Connector to VGA Adapter, or compatible third-party cables and docks—you’ll be able to watch your iPhone 4’s video on a TV, projector, or other external video device. (A couple years back, Apple changed the video circuitry in the dock-connector port, so older video-out accessories won’t work with recent iPhones and iPods.)
However, as with the iPad, there are some significant limitations here. The biggest is that you can’t project everything you might see your iPhone’s screen—only particular apps provide video output, and that list of apps is fairly short: the video mode of the iPod app, the slideshow mode of the Photos app, some video content displayed in Safari, and the YouTube app. (Apple’s support document about video output also lists the Keynote app, which is currently available only for the iPad.) I assume that, as with the iPad, developers will be able to take advantage of this feature—for example, with the iPhone version of the Netflix app—but for now your choices are limited.
