BuddyPress.org

Try this instead:

function wirelab_check_activity_login() { 
	if ( bp_is_activity_component() && ! is_user_logged_in() ) {
		wp_redirect( get_option('siteurl') . '/wp-login.php' );
		exit;
	}
}
add_action('get_header', 'wirelab_check_activity_login');