To clarify, don't don't don't settle for connecting your ipod to the rcd510 via the headphone socket. Frankly that would be a **** solution. You would still have to use the ipod to control music which would be dangerous and old fashioned.
The ipod cable mentioned above will allow you to control the ipod from your rcd510 touch screen and also from your MFSW.
It should cost less than 200HKD, prob even cheaper since stuff in HK usually cheaper than here, ie should be an easy point to negotiate with your dealer to give it to you for free. Good luck
