**Cost**
“OEM vendors could likely add this sensor to their handsets for just five dollars”
reviewscnet/eye-tribe-shows-off-working-eye-tracking-on-a-mobile-phone/
If modifying the device to add eye-tracking only adds 5 dollars to the manufacturing cost, then I’m sure that at least one of the smartphone, tablet, notebook, and laptop manufacturers will make the supposedly easy camera modification.
**Eyes + consecutively touching the same few buttons**
On certain tasks, it might be convenient and fast to have the option of touching “single tap where I’m looking”, and “swipe up where I’m looking” buttons. You would only need one or two buttons that are close to you (kind of like the Android Navigation Bar buttons at the bottom).
Look, touch an easy-to-reach spot, look, and then touch the same button again. You don’t have to keep changing your hand and finger positions between each tap.
Besides the three default buttons in the Navigation Bar, you could add “single tap where I’m looking”, and “swipe up where I’m looking” (to perhaps simulate a Page Down for reading) buttons, and those alone should allow you to do a lot of things).
Vertical touchscreen
If you have a vertically propped up tablet with an external keyboard, you could remap a keyboard button to be the “tap where I’m looking” button.
