California has an exception for hearing aids and other similar devices, but it’s unclear if transcription aids count, or if this has been tested in court. https://codes.findlaw.com/ca/penal-code/pen-sect-632/ (Not a lawyer, this is not legal advice.)

If it were ephemeral? Would that change this? Say recording the meeting locally a 5 minute frame then updating a meeting summary?

Do you mean ephemeral, or are you actually wondering about something implanted under the skin? I'd think/hope if it goes under the skin, it ends up in "hearing aid" territory. I'm less sure about if it doesn't persist.

it's more likely in cochlear implant territory (there are different laws and regulations for implants vs aids depending on locale)

Yup, typo, sorry

Two/all-party consent are hacky workarounds for the actual harm being inflicted (valid goals including not having your microwave inform Google's ad servers, not recording out-of-context jokes as evidence to imprison people, ... -- invalid goals caught up in the collateral damage include topics like the current one about hearing issues (note that a sufficiently accurate transcription service has all the same privacy problems 2-party consent tries to protect against, maybe more since it's more easily searchable)).

I'd be in favor of some startup pulling an Uber or AirBnB and blatantly violating those laws to the benefit of the deaf or elderly if it meant we could get something better on the books.

What did your own research turn up?