Here are iOS Objective-C headers as derived from runtime introspection.

The headers were produced using RuntimeBrowser for iPhone.

You can use the headers this way:

NSBundle *b = [NSBundle bundleWithPath:@"/System/Library/PrivateFrameworks/Message.framework"];
BOOL success = [b load];

Class NetworkController = NSClassFromString(@"NetworkController");
id nc = [NetworkController sharedInstance];

NSLog(@"-- IMEI: %@", [nc IMEI]);

You can search the headers with github search:

https://github.com/search?type=Code&q=repo:nst/iOS-Runtime-Headers+radar