What would an empeg iPhone/iPod app do exactly?

If you just want basic control then reskinning the HTML interface to be suitable for such a small screen would do.

Reimplementing an empeg style interface for the iPhone/iPod wouldn't be viable because of the refusal of Apple to approve it and the fact that the interface of the empeg is what is special about it. That UI and underlying code is what took all those man years to write.