Most of what I (and in my experience many people) want a voice assistant for, is setting+ending timers... which for me happens mostly in the kitchen, while I'm simultaneously holding a hot pan or hand-tossing a salad or paper-towelling off some raw chicken. In none of those cases would I want a ring anywhere near my hands, let alone a smart ring. (And nor, in half of those cases, is it convenient/hygenic to use my oven timer.)

That being said, we could solve for fully 50% of in-home voice-assistant use-cases just by developing an extremely domain-specific voice assistant that has an extremely small (ideally burned-into-a-DSP) voice model that only knows how to recognize commands to manage kitchen timers. If such a device existed, and was cheap enough that you could assume anyone who wanted this functionality would just buy one, then this would make truly hands-free activation of a "real" voice-assistant much less necessary, as there'd be far fewer user-stories that would really "need" that. The rest of those user-stories really mostly could work with some kind of ring / belt buckle / shirt comm badge / etc.

If you want to relax some constraints, I made something similar for $10: https://www.stavros.io/posts/i-made-a-voice-note-taker/