According to Erica at TUAW, the 1.1.1 iPhone Firmware has references to com.apple.mobile.nike, which leads us to assume that the iPhone and Nike+ Sport Kit is going to work together soon.
In fact, this Nike reference was found in LingoToAccessoryMap.plist, so according to Erica, it's "definitely going to be a supported accessory". Looks like someone at Apple heard our challenge and decided to make us all very happy. Because seriously, why force people to buy another flash-based iPod when you've got a flash-based iPod in your iPhone? That's exactly the kind of practice we frown on. Can someone with 1.1.1 and a Nike+ sport kit test this out to see if it works now and email me?
Update: Reader Jake tells me it still doesn't work with the iPhone. Thanks Jake!