ESP8266

A compact WiFi module that adds network connectivity to an Arduino, driven over serial with AT commands. It is genuinely capable — the ESP8266 is a full microcontroller in its own right and can be programmed directly instead of used as a peripheral. Two warnings that account for most failed first attempts: it is strictly 3.3 volts on both supply and logic, and 5V will destroy it, and it draws current spikes during transmission that an Arduino's 3.3V pin cannot supply. Use a separate 3.3V regulator. Adds 2.4 GHz WiFi to any microcontroller; Can also be programmed directly as a standalone board; Simple AT command control over serial; Very low cost for network connectivity