<?php
 // The following snippet of code wraps all of bp-activity-subscription-main.php

global $current_user;
get_currentuserinfo();
$this_user = $current_user->id;
//var_dump($this_user);

$allowed_users = array(1, 2, 3);
if(in_array("$this_user", $allowed_users)):

// all page code

endif;
?>