You don't have a chance. Eye-tracking has been an integrated part of VR headsets for years, since the 80's, and is well and truly sealed up with patent protection. That there are no consumer-ready, plug and play products on the market today is actually a reflection of this fact, not a consequence of omission. The people with these patents are using them in industrial/medical/military/marketing applications - but the consumer version of this tech is well and truly on its way.

Once the glasses-computing wheels start to turn for consumers, expect to see integrated eye-tracking become a stock standard.