Does This DAC exist?

I am looking for a DAC/Headphone amp that is portable, and that captures the pure signal from an ipod via the multi-pin plug and runs it through a much better DAC than what's included in Apple products. This combined with a much better headphone stage, with a rechargeable lithium battery and small enough to carry on airline travel is what I want. These seem to exist with USB compatibility but not the standard size USB plug that the Apple devices use. Am I missing something here? Seems like a no brainer to me. Think how the Wadia 170 & 171 transport works with a separate DAC and headphone amp. Combine these three into a portable ipod sound system and I think you'd really have something cool.