I can't find my notes / the link, but a guy built a system where he wears a little clip microphone device with a giant SD card and it records every conversation that he's in, everything that he says. Then at night he exports all that, transcribes it, embeds things, links it, etc. So it's basically OTS hardware combined with software infra he hacked together.

There are privacy implications for others, of course (I wouldn't want my interactions to be recorded) but setting that aside, the utility / interestingness of this is just staggering; and it's something anyone can basically hack together a shitty version of for a hundred bucks or so, using commonly available tools and software APIs.

I bet it's a really good version of something like this. Hard to see getting over the privacy hurdle, but you can imagine ways that could make it more palatable. Someone's going to do it, whether we like it or not.