Is it possible by any means to have a game developed for iPhone using the iPhone sdk on Windows?
Though it is against Apple's policy, you can install OS X into a virtual machine and develop an app that way. And if you can manage it, you technically can write the code and such on a Windows machine; it is, of course, only text. But the compiler, SDK, etc. is completely OS X-only.
You can also look into other ways to make iPhone games, such as the Unity engine, or Flash (I know at one point they compiled to iPhone games, I think they have since discontinued that)
See this question on stackoverflow.com.
Even if there's some way to do it with virtual machines, jailbroken phones and so on, I can't believe the hassle would be worth it. The time you spend dealing with all the issues is time that you won't have to improve the game.
If you're using a cross-platform development environment like Unity, you'll be able to do most of the development on Windows, but you'll still need a Mac in order to deploy to the phone for testing or release. (And testing on the device is vital: a finger on a touch screen is not like a mouse pointer on a window.)
It's not as if you need a powerful machine to develop an iPhone game: a Mac Mini for $699 will do just fine.
I was looking for a solution to develop apps on Windows. In the end I bought a Mac mini and I am glad I did. The Mac and the develop tools are working just fine. The time I saved figuring out configuring Windows/Virtual machines/OSX and so on I spent on actually developing Apps.
Airplay SDK claims to allow you to develop in Visual Studio on a Windows PC. I have not tried it out, so no idea how well it works.
The Adobe AIR SDK 3.3 allow you to build iOS app on windows platform: http://helpx.adobe.com/flash-player/release-note/developer-relese-notes-11_3.html
However, you have to code your app/game in ActionScript but you can extends the AIR SDK functionality through Adobe Native Extension (ANE).
Marmalade is a good engine which can easily be integrated with Visual Studio. So you can develop for iOS, Android, Bada, WebOS, Windows etc. from single code. You would need a Mac to upload the ipa file though, but i guess it'll be easier since you only need it once. I am using it so I can tell you it works good and now with version 6.0 you can also develop in HTML5 using phonegap API.