ESP8266 ESP-01 WiFi module

The ESP8266 is an impressive, low cost WiFi module suitable for adding WiFi functionality to an existing microcontroller project via a UART serial connection. The module can even be reprogrammed to act as a standalone WiFi connected device – just add power!
802.11 b/g/n protocol
Wi-Fi Direct (P2P), soft-AP
Integrated TCP/IP protocol stack
This module is a self-contained SOC (System On a Chip) that doesn’t necessarily need a microcontroller to manipulate inputs and outputs as you would normally do with an Arduino , for example, because the ESP-01 acts as a small computer. Thus, you can give a microcontroller internet access like the Wi-Fi shield does to the Arduino, or you can simply program the ESP8266 to not only have access to a Wi-Fi network, but to act as a microcontroller as well, which makes the ESP8266 very versatile.