Hi Laura, I don't have a recommendation for a bluetooth speaker as my car has bluetooth. I just wanted to comment on this new law, as a Washington resident, I think it is a good one! I know some people with mixed feelings about it but also know every time I get cut off, I think "they're probably on their phone" and they usually are. It could also be that Seattle drivers aren't the best.
(Hey, I can say that, I am one but at least I know how to go the speed limit).
Also, I asked a police officer about the law and he said they can't pull you over for talking with your phone to your ear, but if you commit a driving infraction AND you are talking on your phone, you will get a ticket for being on the phone in addition to whatever else you did wrong. Not sure if it's the same in California.