byte sensorPin = 3;
byte indicator = 13;
void setup()
{
 pinMode(sensorPin,INPUT);
 pinMode(indicator,OUTPUT);
 Serial.begin(9600);
}
void loop()
{
 byte state = digitalRead(sensorPin);
 digitalWrite(indicator,state);
 if(state == 1)Serial.println("Somebody is in this area!");
 else if(state == 0)Serial.println("No one!");
 delay(500);
}