Jetpack::is_user_connected PHP Method

    public static function is_user_connected($user_id = false)
    {
        $user_id = false === $user_id ? get_current_user_id() : absint($user_id);
        if (!$user_id) {
            return false;
        }
        return (bool) Jetpack_Data::get_access_token($user_id);
    }

 /**
  * Synchronize connected user role changes
  */
 static function user_role_change($user_id)
 {
     if (Jetpack::is_active() && Jetpack::is_user_connected($user_id)) {
         $current_user_id = get_current_user_id();
         wp_set_current_user($user_id);
         $role = Jetpack::translate_current_user_to_role();
         $signed_role = Jetpack::sign_role($role);
         wp_set_current_user($current_user_id);
         $master_token = Jetpack_Data::get_access_token(JETPACK_MASTER_USER);
         $master_user_id = absint($master_token->external_user_id);
         if (!$master_user_id) {
             return;
         }
         // this shouldn't happen
         Jetpack::xmlrpc_async_call('jetpack.updateRole', $user_id, $signed_role);
         //@todo retry on failure
         //try to choose a new master if we're demoting the current one
         if ($user_id == $master_user_id && 'administrator' != $role) {
             $query = new WP_User_Query(array('fields' => array('id'), 'role' => 'administrator', 'orderby' => 'id', 'exclude' => array($master_user_id)));
             $new_master = false;
             foreach ($query->results as $result) {
                 $uid = absint($result->id);
                 if ($uid && Jetpack::is_user_connected($uid)) {
                     $new_master = $uid;
                     break;
                 }
             }
             if ($new_master) {
                 Jetpack_Options::update_option('master_user', $new_master);
             }
             // else disconnect..?
         }
     }
 }