I'm wanting to use my iPod to record from a headphone input. Is there an accessory that will allow me to do that?

I thought the headphone jack is OUTPUT only. All other inputs must be through the dock and a third party adapter.

Some of the older iPods (3rd-gen, with the four buttons above the scrollwheel) had the ability to use one of the headphones (the left one, I believe) as a microphone. You could go into the firmware of the iPod and record short, ~10 second clips of audio. It wasn't great, since you had to speak directly into the headphone (it wouldn't record ambient noise, like a lecture hall or anything).

Belkin offers a microphone adaptor that may or may not work with your particular model of iPod:

http://catalog.belkin.com/IWCatSectionView.process?Section_Id=2062

there are 3rd party addons to allow to do this, belkin do 1, kensington too i think