Plugin to hide posts/pages

I am looking for a plugin to hide posts/pages. Ideally it’s not a registered-user only scripts that stop viewer at the front gate. What I’m thinking is to use the category feature of WordPress. Category is like “label” as in gmail. I want a check box in the add category page such that if it’s checked then that category (or label) when applied a post/page will be hidden from non-registered users. Ideally a customizable message can be displayed. A further step would be a combo box in the category setup page such that different level of users can be assigned to allow viewing a category of posts. At the end this takes away the hassle of password protecting pages/posts, I just have to tick a category to any post/page to hide them. Of course if you want to the pwd protection feature can still be retained by adding it back on the category setup page, i.e. one master pwd for a category, isn’t it nice? Any php coder there watching?