The Notifications module enables sending of notification messages using notification providers. Kentico CMS comes with a built-in e-mail notification gateway. However, you can create your custom gateways, such as an SMS or ICQ provider.
Please note that for one event, users can obtain notification messages from multiple providers. There are three built-in events (document created, document updated, document deleted) and only the first is enabled by default. However, you can create and use your custom ones.