NGUI DisplaySize

DisplaySize.cs

/*
 * Modified this guys code - http://www.zedia.net/2013/ngui-unity3d-getting-screen-size/comment-page-1/
 */
public static class DisplaySize
{
    public static float ScreenHeight(this Transform t)
    {
        UIRoot root = t.root.GetComponent<UIRoot>() ?? NGUITools.FindInParents<UIRoot>(t);
        float ratio = (float)root.activeHeight / Screen.height;
        return Mathf.Ceil(Screen.height * ratio);
    }

    public static float ScreenWidth(this Transform t)
    {
        UIRoot root = t.root.GetComponent<UIRoot>() ?? NGUITools.FindInParents<UIRoot>(t);
        float ratio = (float)root.activeHeight / Screen.height;
        return Mathf.Ceil(Screen.width * ratio);
    }
}

Turns out NGUITools.screenSize is the way to go.