The GearVR has a micro USB port on it that can be used for a number of different things. The trick is to plug in the USB device *before* you plug in the phone! We use the following type of adapter in our GearVR’s to connect up any regular USB-Type A device.
This allows us to power the fan for extended game playing or movie watching (makes the battery last longer) or to take screen shots by connecting a keyboard – you just need to Print-Screen and the screenshot will show up in the Phone’s screenshots folder. You can connect up any HID USB device.