I have an iPhone 4. I just got a JVC head unit for my truck. The sound quality is much better when I use the USB connection, verses the head phone jack. The problem is that I can not control my iPod on my iPhone from my phone, I have to use the HU to scroll through the iPod. Is there an app or device that will allow me to still use the iPhone to change songs, or am I stuck using the HU? Thanks!