>>pinetr+q51
It uses the phone's microphone (Android OS limitation), so if it's Bluetooth in the car, it should pick up everything (just like the people in the next car over can hear your conversation, fyi), but if it's a Bluetooth headset, I don't think it will pick up their side.
Audio quality is very good. By all means test it out in different configurations before relying on it.
A native implementation would still be better. I hope the GrapheneOS devs can pull it off.