HEXR make bike helmets that are 3D printed to fit your actual head. I was their senior iOS engineer, freelance, from January 2020 to May 2021.
I built the ARKit-guided capture flow. It directs you along a virtual path so you can film your own head, at home, on a phone, and end up with something a photogrammetry pipeline can actually use.
The detail that makes it work is scale. A known-scale marker on the fitting cap gives the reconstruction millimetre-accurate metric geometry rather than a correctly-shaped model of unknown size. Shape alone isn't enough when the output is a physical object printed to a tolerance and strapped to someone's head.
I streamed the captured frames into the 3D reconstruction pipeline and integrated the GraphQL backend. It shipped to paying customers: you scan at home on your phone, and a helmet fitted to your own head arrives in the post.
This one was mine end to end, which isn't true of most commercial work and is worth saying plainly when it is.