ESP8266 is a great small WiFi module that carries a microcontroller which can be programmed to do basic IO controls. Having WiFi functionality gives number of possibilities to access module remotely where you can control things withing reach of your network coverage. Rui Santos suggests building a simple Android app which could be used as control panel to ESP module.
In his tutorial he goes through necessary steps of programing ESP8266 module with LUA script and so building Android application with MIT App Inventor. App Inventor is very easy to use and you are able to create simple applications within hour. The app building consist of GUI designed and visual code blocks (similar to scratch on Raspberry Pi). In his example he demonstrates how to control two LEDs from Android app. The code can be easily expanded for more functionality in necessary.