Notification will be shown based on user's context. I personally think mood tracking etc. will also be used by facial detection eventually.
Clip from the patent below:
"In some embodiments, data from multiple sensors or other input elements of the computing device can be aggregated to obtain a more accurate and/or detailed understanding of the context of the device. For example, captured image data can be analyzed to determine that the user is not looking at the display element of the device, motion and orientation data captured by inertial sensors can be analyzed to determine that the movement of the device corresponds to a user\'s gait, and touch sensor data can be analyzed to determine that the user is grasping the device."
Full patent application here: https://www.google.com/patents/US20170102916