iPod UART connection

I am looking to interface the Arduino to the ipod dock connector using the UART TX/RX lines and a program on the iPhone.
It is my understanding that the communications be in 3.3v logic and 5v logic could damage the iPhone/iPod. How would I step communications down to this voltage?

You can use a voltage divider to reduce 5V down to 3.3V. As for going the other way (3.3V-->5V), you probably don't have to do anything as the Arduino should recognize 3.3V as a logic "high".