int heatRelay =  2;  
int overrideButton = 7;
int inByte;
int counter = 0;
int counter2 = 0;
boolean heat;
boolean override;

void setup()   {  
  Serial.begin(9600);  
  pinMode(heatRelay, OUTPUT);  
}

void loop() {
   if (Serial.available() > 0) {
     inByte = Serial.read();
     switch (inByte) {
       case 49:
        heat = true;
        break;
       case 48: 
        heat = false;
        break;
       default:
        break;
     }
   }
   override = digitalRead(overrideButton);
   if (override) { heatOn(); }
   else if (heat) { heatOn(); }
   else { heatOff(); }
 }

void heatOn() {
  digitalWrite(heatRelay, HIGH);
  return;
}

void heatOff() {
  digitalWrite(heatRelay, LOW);
  return;
}