I found some open-finger gloves that I stuff with a regular pair of gloves and it works pretty well.

Still not as good as mittens though.

Riding with an ipod I have no experience with, so you'll have to ask other people. My gut is that gloves will only go so far in their ability to keep your hands warm and still allow you the ability to push tiny buttons.

Warmth is given by ability to trap air effectively, so warmer gloves/mittens tend to be more "puffy" -- which pretty much means those 2 things are always somewhat competing.