What Is an Accessory?
What do we mean by accessory? I define an accessory as any external hardware device that connects to the iPhone via the Lightning connector at the bottom of the phone or via Bluetooth 2.1+EDR wireless signal, i.e., standard Bluetooth. Connecting electronic equipment to an iOS device by either of these means requires the developer to be part of Apple’s MFi program. You can, of course, connect other accessories to your iPhone through Wi-Fi, Bluetooth 4.0 Low Energy (BTLE), and, with a little work, the headphone jack.
The Apple MFi (Made for iPod/iPhone/iPad) ...