Step 1: Get the stuff
Ok, what we need now is a cheap AD2P bluetooth headset, you can buy one on ebay for exemple. You'll need an enclosure for your project too, I tought it was cool to use a vintage tape as my enclosure.
Step 2: Taking appart the headset
Take appart the headset carefully because all the tiny wires are very fragile.
Then cut the headphones wires.
Step 3: Put evrything in the case
Step 4: Adapt th impedence
The resistors are 180Ohms.
Step 5: Close the case
I've glued the controls buttons on the head of the tape case. (as shown).
Step 6: Pair it with your device
Now you have to pair it with your bluetooth device, and start playing some music.
Step 7: Enjoy !
Enjoy a cool ride in your old car, with cool music and no wires !