How to tell if my app is running on an Android or iOS?

I've hooked up the OpenFeintFacade for android to my app. I was hoping at runtime to remove the initialzation and hide the guibutton for activating it if the app is running on an iPhone.

Is there something I can test in C# to determine what platform it's being run on?

http://answers.unity3d.com/questions/37531/unity-mode-from-c/37537#37537

http://unity3d.com/support/documentation/Manual/Platform%20Dependent%20Compilation.html