Using the powerful ESP8266 IC, the ESP-13 Wifi Shield adds much more than just plain wifi to your Arduino. It has an 80MHz processor and can also act as an access point or web server. An excellent way to get into the Internet of Things.
• Integrated TCP/IP stack
• Simple AT command interface with Arduino main board
• Can be programmed directly with Arduino IDE (separate programmer needed)
• Web configuration interface
• Switches on shield to disconnect from Arduino
For More info on Arduino.