Google is looking to possibly add detection capabilities for onlookers who may be looking over the users shoulder in future either to Pixel cameras as feature of an app they can add as needed

https://www.pcmag.com/news/357630/google-researchers-add-spying-eyes-detection-to-a-smartphone

If someone else is looking at your screen the front-facing camera will detect it and alert you.  We are all used to seeing people walk around hunched over and completely consumed by what’s happening on their phone display. Many accidents have happened because of it, and it proves we do not pay attention to what’s going on around us when using a smartphone. That includes when other people are looking at your screen.

Two Google researchers believe they have come up with a good solution to the spying eyes problem, though. It takes the form of an app which relies on access to the front-facing camera on your phone.  We are all used to seeing people walk around hunched over and completely consumed by what’s happening on their phone display. Many accidents have happened because of it, and it proves we do not pay attention to what’s going on around us when using a smartphone. That includes when other people are looking at your screen.