This does bring up an interesting point though... I honestly wonder why Apple refuses to release an SDK for the iPod. I know a lot of people just want tunes to go in their pocket, but there are all sorts of handy tools and games that people would happily code and give away for free if they only had the tools to make them. A calculator would be a simple but handy start.
Personally, besides tweaking the interface a little, I'd love to have a crack at porting the unabridged Oxford English Dictionary to the iPod. We're talking about the multi-volume set that you'd be hard-pressed to fit in a Volkswagen here! It would probably take about 600-800 MB of space, so it's not the sort of thing you'll see on a palm any time soon. I suppose the OED might be overkill, but you might as well aim high! Any decent dictionary would be nice to have for those of us who read while listening to tunes.