An SGF editor or player would be impractical, since the clickwheel is one-dimensional, and you'd have to scroll through 361 points at best.

An SGF viewer such as EDA Go Reader could work. You could replay game records by scrolling the wheel. So yes, it is possible to make a go application for the iPod, but the input method would restrict it to a simple sgf player. To the best of my knowledge, no such programs exist yet for any iPod. However, making such a program once you have the development kit is fairly trivial: all you have to do is make an sgf parser and a simple board. It wouldn't even need to understand variations.