This project is about calling to your Arduino using Twilio & Yaler.net services.
Twilio is a Web service that turns everything into a phone, and Yaler.net enables Web access to embedded devices behind a firewall, NAT or a mobile network router. Here it enables Twilio to access the voice.xml file on the Arduino, which is located in a local network and therefore does not have its own public IP address.
In this tutorial, the author uses temperature sensor in order to advise the current room temperature to the caller. But author says “any other sensor would do as well” (for example, such as smoke detector)
Ethernet shield (WIZnet’s W5100 is embedded) is responsible for the Internet connection with IoT servers.
For more detail about this project, click here.