Restrict category access to certain IPs

Hi,
Does someone happen to know where to find a plugin (if any) where we can restrict category access to certain IPs?
My case is I’m maintaining a blog for my department and I need posts in certain categories only be accessible from my staff’s computers, without having them to login to view them.
I know basic PHP to hack my theme and selectively hide categories on-site using $_SERVER[‘REMOTE_ADDR’] but it will still be accessible from the blog feed, while using .htaccess will restrict unmarked IPs entirely.
Can someone please help me?