The author wanted to create a ‘IoT’ thing with Arduino Ethernet Shield (W5100) and developed this LED Christmas tree. By combining G-mail API with Temboo’s Arduino code, he can connect the tree to the Internet and count the number of unread e-mail message.
The number of unread emails in his gmail inbox is got by the Ethernet shield using the Temboo library (which helps you to communicate with a lot of APIs). Then, the Arduino board draws a Christmas Tree on a 16×32 LED matrix. The number of red LED is equal to the number of unread emails.
You can see more detail from Instructable.com