Apple has been granted another patent (number 20170187855) for a head-mounted display. This one involves retaining a portable electronic device — almost certainly an iPhone — with the display.
The invention would allow you to couple and decouple a portable electronic device such as a handheld portable electronic device with a separate head-mounted device, temporarily integrating the separate devices into a single unit). The iPhone may be physically coupled to the head-mounted device such that it can be worn on the user's head.
The iPhone may be operatively coupled to the head-mounted device such that the portable electronic device and head mounted device can communicate and operate with one another. Each device may be allowed to extend its features and/or services to the other device for the purpose of enhancing, increasing and/or eliminating redundant functions between the head-mounted device and the portable electronic device.
Apple has been granted other patents for head-mounted displays, including patent numbers 9,482,869, 9,646,574 and 8,957,835,
Of course, Apple files for — and is granted — lots of patents by the U.S. Patent & Trademark Office. Many are for inventions that never see the light of day. However, you never can tell which ones will materialize in a real product.