Looking for the easiest and most reliable iPod or iPhone music integration module

I've been searching and reading the solutions people have implemented but thought it best to ask everyone what they recommend. I have an 01' with HK and I'd like to be able to use an iPod or perhaps my iPhone as a music source.



I'm also ok with it living in the trunk long term with whatever device makes it accessible. The key to me is easy to use and reliable. Any recommendations are welcome and appreciated!