This is simple module that adds a trigger when a user password is updated. It uses the built-in trigger module from Drupal core.
The trigger can be setup at build/trigger/node.
An action included in the Password Trigger named "Send password change notification e-mail" can send a tokenized email to the affected user. The email notification is sent to the email address set on the account before the password change in case the password change also includes an email change.
The email action can be setup at admin/settings/actions/manage.