Guitar pedal to control iPod

Hello everybody,

As a favor for a friend of mine I'm building a guitar pedal that will control his iPod (he uses it for loops while playing). I've seen a couple of iPod accessories driven by Arduino, but my question is does anyone know if iPods need 3v or 5v for the serial communications (I've seen project examples using both)? If it needs 3 I would hate to fry his iPod. If it needs 5 I would hate to have a unreliable device.

Thank you!

Loren