Recently I wrote a Magento extension called ActionLogger, inspired (thematically) by the “Logging of Administrator Actions” feature available in Magento Enterprise. ActionLogger is pretty simple extension, working on pretty simple but powerful concept of Magento controllers predispatch action.
All you need to do is to create event observer/observers for “controller_action_predispatch” event. This event is fired on every controller action call.
For example, if your store is located on url http://magento-1501.net url, and you go to url like http://magento-1501.net/electronics/cell-phones this will call action “view” from controller “category” from module “Mage_Catalog“. Simple logic/tracing would point this to be app\code\core\Mage\Catalog\controllers\CategoryController.php file and its viewAction().