How to redirect toward a specific node from front-page in Drupal 7?
page--front.tpl.php simply allows you to create a different page template than the default page.tpl.php template. When drupal loads the homepage and there is a page--front.tpl.php it will laod that template instead.

If you want to check if you are on the homepage you can use the is_front variable. It would be best to use hook_boot in a custom module. 

hook_boot(&amp;$vars) {
  if($vars['is_front']) {
    // do your redirect
  }
}


You can use drupal_goto() to handle the redirect.