If any iOS developers are wanting a good repo to follow, I believe HeadGazeLib is about to take off.

There's been a few articles about how eBay is using head tracking to allow for hands free shopping (huge for accessibility!) If the rumors are true, then Apple should be announcing many more devices that support Facial Recognition (like the iPhone X). If they do, then there will a huge surge in games/apps that tap into that technology.

HeadGazeLib makes it super easy to incorporate Head Tracking in your apps, so I think with all the publicity, it will quickly rise to the #1 head tracking "add-on".

https://github.com/eBay/HeadGazeLib