Yes an iPhone can receive serial data but you have to register as a developer to write any code on an iPhone. Then the only way you can get this code onto the iPhone is to submit it to Apple and have them put it in the Apps store.
Actually you don't even have to submit it to the app store, you can deploy the app straight to your iPhone/iPod if you're registered as a developer. You can write code for the device without being registered as a developer too, you just need to register to get it on the device. But you're sure an iPhone can receive serial data and code can be written to handle it?