AirPlay mirroring is one of the features made available on the iPad 2 that i was hoping Apple would make available for other iOS devices as well, and now they have, if only for the iPhone 4S at the moment.
The addition of AirPlay mirroring was presented as part of the new features of the iPhone 4S at the Apple media event, but perhaps drowned out a bit as more time was spent presenting the new Siri voice assistant. AirPlay mirroring allows you to display the entire screen of your iPhone 4S onto another screen, such as your HD television set, using the built in Airplay feature (requires a TV with AirPlay functionality or an Apple TV). There is also the option of achieving the same thing with without AirPlay needed, using a supported wired dongle, although the main purpose is to be able to free yourself of wires.
AirPlay mirroring could bring amongst other gaming experience on the iPhone 4S to a new level by streaming it to a larger screen while still maintaining the iPhone controls.
I look forward to testing AirPlay mirroring following the release of the iPhone 4S.