Erica Sadun of TUAW has released what is described as an “extremely alpha” version of AirPlayer, a new Mac application designed to allow for video streaming from an iOS 4.2 device to a Mac. According to Sadun’s post announcing the software, the application was made by reverse engineering AirPlay, and creates and advertises a custom Bonjour AirPlay service that pretends to be an Apple TV. The post notes that users do not need a jailbroken…