[lightedman]

"How are the glasses more beneficial than the far, far more durable helmet-mounted cameras"

Helmets add lots of head space - not usable in very tight areas, especially the ones I'm in where you have to breathe out to get through a gap.

"Also, how well do the glasses function underground? Are there pico cells down there to provide connectivity?"

They work fine. Typical 4k action glasses actually have decent low-light performance (mine work great with the fluorescent reaction of rocks from a ~200mW output UVC lamp) and I just upload once I'm above-ground and have the memory card put into my laptop.