Read data from mobile phone

I would like to write a program for Arduino BT that waits until a mobile phone sends it some data over bluetooth and then does something (like switches on the LED). I understand that BT communication can be done over serial interface, but I am wondering if it needs any preconfiguration on the Arduino side. I copied this code from one of the examples and adapted it, I'd like to know if I have to add something to the setup method:

int FLASH=13;
int val = 0;

void setup()
{
  pinMode(FLASH, OUTPUT);
  Serial.begin(115200);
  
}

void loop()
{
  if (Serial.available())
  {
    val = Serial.read();
    if (val >= 0)
    { digitalWrite(FLASH, HIGH);
    } else
    { digitalWrite(FLASH, LOW);
    }
  }
  
  delay(100);
}

Thanks in advance.