You must have observed this new feature of Facebook, now while posting any status update on Facebook Timeline you can manually set who can view your stream. Now you can enable same type of feature in your BuddyPress site.
Role Scoper, a free WordPress plugin allows you to gain more control over reading and editing permissions in your WordPress site. Using this plugin you can assign restrictions and roles to your specific WordPress pages, posts and categories.
Ghostery is for all those users who care about their online privacy and it has been engineered keeping privacy as its primary goal. Ghostery use is completely anonymous without any registrations, sign-ups etc. Even it never places session cookies in your web-browser and neither its application nor evidon receives any kind of data from its users unless its users opts-in to participate in GhostRank whose data is anonymous and it is never used for advertising or targeting purposes, and is only shared in an aggregated, non-personal, statistical form.
There are many different plugins in WordPress Plugin Repository that allows you to limit your website access in different ways. Now this tutorial explains you limiting your WordPress site access for logged in or allowed by IP addresses.
WordPress allows you to publish password protected posts. You can add password protection in your blog post by using visibility option present in the Publish meta box on post’s add new/edit page; using this feature you can set a separate password on your post and share it with selected users. Now this tutorial explains you how you can set a global password which is applicable with all your password protected posts and pages.