This was exactly what I was looking for, in order to create a private site, accessible only to family and relatives.
There is only one significant problem I encountered - my site is still in development, on my local machine, therefore the home URL is http://localhost:<port number>/wordpress.
After I installed the plugin, whenever I log in (does not matter if I log in as admin or subscriber), the port number from the URL is removed (it becomes http://localhost/wordpress, and I get an error page instead of the site Home page.
Then, when I add the port number back to the URL, the home page is displayed and I am logged in correctly.
It would be nice if this could be fixed soon.