On the watch there is a setting under BT to play phone audio on watch. Then it will pair like a normal BT device. (Unless you have changed the BT settings on phone for the device to not use the phone profile, in which case I had to unpair from phone BT settings and repair.) When set to play phone audio on watch, I often have to disable that to successfully connect phone to my car, though sometimes I can get phone to switch to car from the BT quick settings menu. Also when using paired with watch for phone audio if you answer on phone it does use phone speaker, however the in call audio source (earpiece, speaker, BT) shows as BT so the proximity sensor doesn't work until you select phone earpiece. I have Nexus 6.