Point out what [constitutionally valid] law it’s broken; if it’s audible to the ear from a public location in San Francisco (or anywhere in the US) then you’re allowed to record it (similarly if you can see it from a public vantage point, then you can photograph it).

If you weren’t it would be legally impossible for any two people to leave two voice messages simultaneously while in earshot of each other. You also couldn’t use Spotify in public ever.

You can certainly get in trouble for the uses you put that recording to, but as the OP isn’t selling or rebroadcasting and would have a solid fair use defense for any incidental copyright infringement, I don’t see any colorable claim that anyone this thing can hear has any reasonable expectation of privacy from it.

BTW, it’s making a very good point about actual surveillance equipment that is quite possibly installed all around you.