Various options for redirecting to a "Coming Soon" page with WordPress.

coming_soon.php

/*
	1. Create a page called "Coming Soon" with the slug "coming-soon". 
	   If you use something different, be sure to update the code below.
	
	2. Copy just one of the blocks of code below to a custom plugin or your active theme's functions.php.
*/

//redirect non-users to the coming soon page
function coming_soon_redirect()
{
	global $pagenow;
	
	if(!is_user_logged_in() && !is_page("login") && !is_page("coming-soon") && $page_now != "wp-login.php")
	{
		wp_redirect(home_url("coming-soon"));
		exit;
	}
}
add_action('template_redirect', 'coming_soon_redirect');

//redirect non-admins to the coming soon page
function coming_soon_redirect()
{
	global $pagenow;
	
	if(!current_user_can('manage_options') && !is_page("login") && !is_page("coming-soon") && $page_now != "wp-login.php")
	{
		wp_redirect(home_url("coming-soon"));
		exit;
	}
}
add_action('template_redirect', 'coming_soon_redirect');

//redirect non-members (requires Paid Memberships Pro) to the coming soon page
function coming_soon_redirect()
{
	global $pagenow;
	
	if(function_exists('pmpro_hasMembershipLevel') && !pmpro_hasMembershipLevel() && 
		!is_page("login") && !is_page("coming-soon") && $page_now != "wp-login.php")
	{
		wp_redirect(home_url("coming-soon"));
		exit;
	}
}
add_action('template_redirect', 'coming_soon_redirect');

//redirect non-users to coming soon page, but allow certain other pages
function coming_soon_redirect()
{
	global $pagenow;
	
	$okay_pages = array("login", "coming-soon", "about", "contact", "faq");
	
	if(!is_user_logged_in() && !is_page($okay_pages) && $page_now != "wp-login.php")
	{
		wp_redirect(home_url("coming-soon"));
		exit;
	}
}
add_action('template_redirect', 'coming_soon_redirect');