Thanks for the input, Bruno, I appreciate it. I'd seen that model but as you say it's out of stock. My most recent attempt at a solution was
this device, which Tom apparently also has. But I'm not very thrilled with it. I could live with it, but the call quality is horrendous, and the person I'm talking to cuts in and out constantly. It's awful. Then there's a single button, so I can only control start/stop playback of music and podcasts, or initiate/hang up a phone call. Lastly I seem to be getting...what did you guys always call it...a ground feedback loop? Basically it buzzes with a little bit of static-y sound, because of the power and audio being connected at the same time to the same device.
So I'm still looking, and it's not going well.
I custom made an iPhone dock with USB charging, aux-out through the dock, and it even charges my bluetooth headset, all in one plug.
Very nice! I like the job you did! That looks like a great solution, and I could see myself getting very fed up with all of this at some point and doing something custom, but I don't trust my ability to pull it off

Ideally, I'd like Bluetooth A2DP, but my car already has Bluetooth for making calls. Do these play nicely together?
I'm not entirely clear what you're asking, but when you connect a bluetooth device to your phone you should be able to specify what duties that device will handle (phone/music).