There are several ways to do this in Wordpress using PHP, as shown here
//redirecionar nao-administradores
function pagina_em_breve()
{
global $pagenow;
if((!is_user_logged_in() || !current_user_can('manage_options')) && !is_page("login") && !is_page("em-breve") && $page_now != "wp-login.php")
{
wp_redirect(home_url("em-breve"));
exit;
}
}
add_action('template_redirect', 'pagina_em_breve');
Alternatively, you can use .htaccess
to redirect every IP different from yours to that page:
Options +FollowSymlinks
RewriteEngine on
RewriteCond %{REMOTE_ADDR} !^123\.45\.67\.89$ # <-- seu IP
RewriteCond %{REQUEST_URI} !em-breve\.html
RewriteRule ^(.*)$ /em-breve.html [R=302,L]
Do not forget to replace with your IP in !^123\.45\.67\.89$