FartometerArduinoProject is one solution that allows you to make fart battle with your friends, showing how strong are your farts and theirs.
This Arduino code allows you to send and receive data between the arduino device and another device such as a smartphone through bluetooth.
For this project, I'm using SparkFun RedBoard, which I bought their Inventor's Kit + RedBearLab BLE Shield, which is the shield for the communication between the devices + Sound detection sensor + Methane Gas Sensor MQ-4.
For getting started with the Arduino board + BLE Shield you should probably take a look at here, here and here.
This project extends GNU GPL v. 2, so be aware of that, regarding copying, modifying and (re)destributing the application.