https://techcrunch.com/2018/10/29/observant-launch/

Observant has found a new way to use the fancy infrared depth sensors included on the iPhone X, XS and XR: analyzing people’s facial expression in order to understand how they’re responding to a product or a piece of content.

Observant was part of the winter batch of startups at accelerator Y Combinator, but was still in stealth mode on Demo Day. It was created by the same company behind bug reporting product Buglife, and CEO Dave Schukin said his team created it because they to find better ways to capture user reactions.