ESP8266 is quite new wireless LUA based microcontroller, it is possible to use it with Arduino IDE as well, which is handy. This module runs at 3,3V and you can connect it into your existing local network or use it as standalone acesspoint / hotspot. It can host web server based control that you can manipulate from any connected device trough web browser. With it’s dimensions of 16x24mm, it’s one of the best options NOW for developing simple wireless IOT devices. The ESP8266 – E12 I´m using for my projects has VCC(3,3V), GND, 17 GPIO’s incluiding serial rx/tx pins and SPI, one ADC and PCB antenna. There is also an option to use this device attached to the breakout board (great for uploading of software before build in to the device where there is not necessary serial connection) or to use all at one board solution as Node-MCU board, which has built in usb to uart shifter, 5v to 3,3V power converter and two useful buttons, one for code upload and one for reset. Possibility to connect SD card straight trough SPI allow’s you to have server big as much as you wish to have.