Trying to rewrite url for a custom module with an extra custom variable using PathAuto
You have a 2-step problem.

1) User friendly URLs

Pathauto is the wrong solution. Setting URLs in custom modules is the job of hook_menu.

function mymodule_menu() {
  $items['product'] = array(
    'page callback' =&gt; 'mymodule_product_view',
  );
  return $items;
}

function mymodule_product_view($id = 0) {
  //Do database call here for product id = $id
}


Using this simple example, you can visit the page product/50. Drupal will then call the mymodule_product_view function with the second parameter (in this case 50) as the arguement.

2) Creating a block to show product information

What you need to get is the product name or id. If that is already in the url you can use arg(2) assuming your URL is "examples.com/product/50". Here is the api page for Drupals arg function.

Ideally you would then do database calls etc. with this arguement within a custom modules block. You can find out how to create a block in custom code here