This tutorial demonstrates how to send SMS alerts using Ruby and the Sinatra framework with the Twilio REST client. The application first configures the Twilio client by reading account SID and auth token from environment variables, then creates an administrator list in YAML format that contains phone numbers for system administrators. When an exception occurs, the `Notifier` module sends a message to each administrator on the list using the `send_sms` method. This process involves creating a Twilio REST client, handling application exceptions, triggering notifications for each entry in the administrator list, and sending a text message with three required parameters: from, to, and body. The tutorial concludes by highlighting additional features of the Twilio Ruby SDK that can be integrated into applications.