Just stumbled on this little feature new in iOS 4.2. While sitting in my drive way, and going through my regular ritual of getting my self ready to drive, I plugged my iPod Touch to my car stereo with the 40 pin USB cable, and up pops a new alert giving me the choice of what speakers I want to connect to, because I’m still in range of my home WiFi network. By choosing the ‘dock’ option, it played through the car stereo speakers, and as soon as I was out of my WiFi range, the option disappeared.
New AirPlay Feature In iOS 4.2 Lets You Quickly Choose Which Speakers You Want To Connect To
iOS 4.2: Quickly Choose Which Speakers You Want Your Docked iPhone/iPod/iPad To Connect To