I'm not sure what other people's hands are like, but mine are pretty big and I can just barely push my thumb against the part of my index finger where I would wear a ring, and doing so renders my thumb useless for any of the opposable things that I usually use my hand for. It's also extremely uncomfortable for my hand and thumb. I've managed to press buttons on my watch with my hands full, but it would literally be impossible to activate this thing with my hands full.

I've worn rings, and they can rotate in place on the hand if they're not perfectly sized, and there aren't any half sizes here, so this would definitely rotate on my finger, making no guarantee that I can even reach the button without adjusting the ring with my other hand, or maybe awkwardly spinning it with my thumb until the button is in reach again.

And it only lasts for 10-15 hours of recording time. And there looks to be a cloud services upsell for better STT than the open source offering on device.

This seems like an early alpha version of something that might be a good idea, but as it is I can't imagine buying one.