You can yes, but you need a mac at some point if you want to make an iPhone game. You will need an Iphone license for Unity, and you need to be a paid Apple developer. Iphone Basic and a single user apple license will set you back around $400 - $500 dollars based on whether or not you take advantage of the Unity 3 discount. Which, is a fairly cheap amount if you think you will make much money with your app.

Follow the steps in the Unity iphone documentation on how to set up you account. Now, here's where you might have to do a little work. If you are building your app on a mac, then you can make your windows standalone and build to the iPhone simply by loading your project in iPhone 1.7 and hitting build (and of course configuring your app for iPhone input). Come Unity 3, you won't have to load your project in different versions of Unity and will just be able to build to both that simply. You will also be able to use Compiler directives to specify which code is built to which version.

If your on a PC. Then you can make your app on your PC and build on a PC, but given you cannot run xCode on a PC, you have to transfer you app to a Mac and run Iphone 1.7 with your app to build it. Then it should all run fine.

Well. To make a game for the iPhone, you will need the iPhone add-on found here: https://store.unity3d.com/shop/

Here: http://unity3d.com/unity/licenses is a comparision of the different Unity licenses. It will show you what you need to create a game for whichever system.