<?php

/**
 * Implements hook_menu().
 */
function foo_menu() {
  $items = array();

  $items['node/%node/check'] = array(
    'title' => t('Checking'),
    'access callback' => 'foo_callback',
    'page callback' => 'foo_body',
    'page arguments' => array(1),
    'type' => MENU_LOCAL_TASK,
    'context' => MENU_CONTEXT_PAGE | MENU_CONTEXT_INLINE,
  );

  return $items;
}

/**
 * Custom callback.
 */
function foo_callback() {
  return TRUE;
}

/**
 * Custom menu callback;
 */
function foo_body($node) {
  return 'a';
}