Do you really need both ends, though? One could be enough to reasonably predict the focus of the other as well - at least enough for the general area for foveation, even if it may not be precise enough for something like aiming. Obviously bespoke hardware would be better, but it could be enough for the entry level.
You need a front facing one for head tracking, one facing your eyes to track your pupils. You can turn your head to the right and your pupils to the left independently!
Blinking to select, how does it filter out natural blinks, and won't that get tiring. Just imagine playing those click thousand times a minute games :)