A new patent application for “Wireless audio output devices,” published Thursday by the United States Patent and Trademark Office (USPTO), describes exactly how Apple's new W1 chip inside AirPods enables zero-configuration Bluetooth pairing. In a nutshell, the charging case that comes with AirPods doubles as a physical pairing interface.
Aside from a built-in battery, the case features its own microprocessor and communications stack, a motion-detecting lid for starting the seamless pairing process with an Apple device and a physical button for manual Bluetooth pairing with non-Apple hardware, like Android handsets.