This is likely the FB job listing: https://www.facebook.com/careers/jobs/a0I1H00000LgnqFUAR/ Looks like all of the difficulty of building a hardware startup, while maintaining all of the downside of being part of a large company.

[IIRC, Cisco used the "spin-in" model to great advantage in order to address some of the downside. However, that was 10-20 years ago, and I don't know any recent examples.]