I don't think you'll find a way to seamlessly build native iOS apps from Windows. Visual Studio has a great development environment for iOS apps but the compilation still has to happen on a Mac. It's more difficult for developers, but Apple tightly controls their entire stack.

And for all of you on the thread who say Windows is a disaster for developers, I'd love to chat with you. I'm the guy for the MSVC C++ front end and code analysis. Either PM me or mail me: my work address is apardoe at youknowthecompany.com