Create a custom module with a form to set/get custom system variables from Drupal. We're going to add custom permissions to access this new page. Bonus: add simple page to count every node for each content type.
Summary
Step 1: create custom module
Step 2: call hook_menu and hook_permissions
Step 3: create custom callbacks for new menus
Step 4: create a Drupal form by code. Form, validate and submit