I'm currently using Erica's code to get hold of the iPhone IMEI number programmatically: https://github.com/erica/uidevice-extension/blob/master/UIDevice-IOKitExtensions.m
This works fine on iPhone 3G and 4, even an iPhone 4 with iOS 5. But when I try it on a iPhone 4S, it returns empty.
Does the code I'm currently using need updating, or is there an alternate method to get the IMEI on the 4S?