simple example of code to connect MQ line of sensors with Android phone

MQ136

#include <MeetAndroid.h>
// http://www.amarino-toolkit.net/index.php/download.html
MeetAndroid meetAndroid;
int sensorValue; 

void setup()
{
  Serial.begin(9600);      // sets the serial port to 9600
}

void loop()
{
  meetAndroid.receive(); // you need to keep this in your loop() to receive events
  sensorValue = analogRead(0);  // read input pin [alalog 0] 
  meetAndroid.send((sensorValue, DEC)); // send result to Android
  delay(1000); // add delay
}