As the recognition happens on the phone rather than in the cloud, the technology can recognize a rude viewer in as little as 2ms. It should also work in different lighting conditions and poses.

There's no mention of whether or not this will ever become a shipping feature. We've asked Google if it can say more about the project ahead of the presentation. However, it's easy to see this becoming an option, even if it's not something you'd want to run non-stop (that would likely kill your battery life). You could turn it on when reading sensitive email or watching a video. This wouldn't prevent people from seeing things in their peripheral vision, but it could encourage peeping types to mind their own business.