The Most Obvious Way for On-Screen Notifications on Moto X
The individual pixels for the notification would turn on (remember Woodside said it had an OLED display) once when the notification came in.
Then use the gyroscope to turn on the notification if the phones is handled.
Anything like eye tracking would be too convoluted and turning on only once would be extremely stupid.
The gyroscope doesn't waste battery, is simple, and works.