I recently bought a phone mount for my Audi A6. It is two parts. One part adapted for my car, the other part is adapted for my HTC Desire. The power is taken from a cigarette lighter connector. Stupid fucking retarded connector not designed for this! So my solution is to hack my car and the phone mount (it is not a car mount for my phone… would look kinda stupid to walk around with a car on the phone all day).
Step 1 is to add a powered USB to my dashboard. Step 2 is to snip the cigarette lighter plug and put a USB connector there instead.
Today I have soldered wires to the cable harness on the Symphony head unit. By using the “S” lead I get power when the ignition key is inserted AND turned. The power remains on until I remove the ignition key. So I can turn the motor off and still charge the phone. But when leaving the car (and taking ignition key out) there is no power to the USB port. Just the way I like it.