The point of this idea is that it would be under control of the individual wearing the glasses. I would most definitely not want it to be syncing to the cloud or some stupid shit like that. The buffer, and the storage, would need to be entirely contained within the glasses (or other device, if it turns out audio is a legally safer way to implement something like this).

As I mentioned in a sibling comment, I'm not against a visual notification of such recording once the "start saving to storage" button has been pressed. At the same time, I realize that the 60 seconds or so leading up to pressing that button is also often vital (otherwise dashcams wouldn't use a rolling buffer). And in such a situation where audio (or video, in applicable jurisdictions) is being recorded only in volatile memory and overwritten when the buffer is exhausted, I don't think a recording notification should be necessary unless the user has actively engaged non-volatile recording. In that sense, it's similar to the difference between streaming and downloading media. Both are technically the same, but the intention of "streaming" is to download the media and decode it without storing it in a non-volatile fashion.

I think you're thinking about this a bit naively, concentrating on the utility without considering the detriments.

Look at social media. WE are the ones who surveil ourselves. Yes, the big social media companies process all that data and use it against us, but we are the ones who give the pictures, videos, and words to them. There's really no good way around this either. I put those same things on my blog and they still get scrapped.

So what ends up being the difference? It's not synced to the cloud, but we put it there anyways. Do you really think most people are just going to take the videos and not share them? Do you think most people are just going to run a NAS at home? In an ideal world, yes. But I don't think we're anywhere near that happening. So a good portion of those videos just get put online somewhere and bad actors have access.

Non-volatile recording doesn't really exist. We're on HN and I'd expect most people here to be familiar with how easy it is to download a streamed video. yt-dlp will do that for a lot more than youtube.