Drupal Commerce is built on top of Drupal 7, Views, and Rules. The fact that it's built on Rules means that you can alter the behavior of your store without changing any PHP code, so changes of behavior for campaigns and changes of behavior for stock management are all within reason.
In this screencast I show how Commerce Stock adds stock management to Commerce, how to add a custom "reorder threshold" to a product type, and then how you can piggy-back a custom rule on that to notify when the stock hits the reorder threshold.
- A simple feature for use with Features Module that packages up the rule and fields demonstrated here is at http://drupal.org/sandbox/rfay/1229306 (or download it as a tarball.) If you'd just like an export of the notification rule, it's attached to this article.
- Node One has done an enormous number of screencasts on Rules. This is just one of them.
- The Rules Handbook