This reads the heading from HMC6352, reads your current location (hardcoded), and your destination (hardcoded), and turns the pin high pointing to your destination

CompassBracelet.ino

//Compass Bracelet GPS

//This reads the heading from HMC6352, reads your current location (hardcoded),
//and your destination (hardcoded), and turns the pin high pointing to 
//your destination

//HMC6352 compass is hooked up this way: SDA is on analog input pin 4, and SCL is on analog pin 5
//To customize, change destinationLat, destinationLon, currentLat, currentLon

#include <SoftwareSerial.h>
#include <Wire.h>
int HMC6352SlaveAddress = 0x42;
int HMC6352ReadAddress = 0x41; //"A" in hex, A command is: 

int headingInt;
int realNorth = 0;
int notificationDirection = 0;

const float destinationLat = 55.597261;
const float destinationLon = 12.979427;
float currentLat = 40.729483;
float currentLon = -73.993513;

//float currentLat, currentLon;
int directionToDestination = 0;

int EPin = 13;//east
int SPin = 12;//south
int WPin = 9;//west
int NPin = 8;//north

SoftwareSerial nss(3, 2);

void setup(){
  // "The Wire library uses 7 bit addresses throughout. 
  //If you have a datasheet or sample code that uses 8 bit address, 
  //you'll want to drop the low bit (i.e. shift the value one bit to the right), 
  //yielding an address between 0 and 127."
  HMC6352SlaveAddress = HMC6352SlaveAddress >> 1; // I know 0x42 is less than 127, but this is still required
  while( millis() < 500) { delay(10); }  // The HMC6343 needs a half second to start from power up
  pinMode(WPin, OUTPUT);  
  pinMode(NPin, OUTPUT);  
  pinMode(EPin, OUTPUT);  
  pinMode(SPin, OUTPUT);  
  Serial.begin(9600);
  Wire.begin();
}

void loop(){
  //"Get Data. Compensate and Calculate New Heading"
  Wire.beginTransmission(HMC6352SlaveAddress);
  Wire.write(HMC6352ReadAddress);              // The "Get Data" command
  Wire.endTransmission();

  //time delays required by HMC6352 upon receipt of the command
  //Get Data. Compensate and Calculate New Heading : 6ms
  delay(6);
  
  directionToDestination = calculateDirection(currentLat, currentLon,destinationLat,destinationLon) * 10;
  Serial.print("dir: ");
  Serial.println(directionToDestination);
  
  readCompass();
  realNorth = 3600-headingInt;
  notificationDirection = realNorth + directionToDestination;
  if(notificationDirection > 3600)
  {
     notificationDirection = notificationDirection - 3600;
  }
  showDirection(notificationDirection);
  delay(500);

}

void showDirection(int heading){
  //North
  if (heading > 330 || heading < 30 ){
    digitalWrite(NPin, HIGH); 
    digitalWrite(EPin, LOW);
    digitalWrite(SPin, LOW);
    digitalWrite(WPin, LOW);
  } 
  //NorthEast
  if (heading > 30 && heading < 60 ){
    digitalWrite(NPin, HIGH);
    digitalWrite(EPin, HIGH); 
    digitalWrite(SPin, LOW);
    digitalWrite(WPin, LOW);
  }
  //East
  if (heading > 60 && heading < 120 ){
    digitalWrite(EPin, HIGH);
    digitalWrite(SPin, LOW);
    digitalWrite(WPin, LOW);
    digitalWrite(NPin, LOW);
  }
  
  //SouthEast
  if (heading > 120 && heading < 150 ){
    digitalWrite(EPin, HIGH);
    digitalWrite(SPin, HIGH);
    digitalWrite(NPin, LOW);
    digitalWrite(WPin, LOW);
  } 
  //South
  if (heading > 150 && heading < 210 ){
    digitalWrite(SPin, HIGH);
    digitalWrite(NPin, LOW);
    digitalWrite(WPin, LOW);
    digitalWrite(EPin, LOW);
  }
  //SouthWest
  if (heading > 210 && heading < 240 ){
    digitalWrite(SPin, HIGH);
    digitalWrite(WPin, HIGH);
    digitalWrite(EPin, LOW);
    digitalWrite(NPin, LOW);
  }
  //West
  if (heading > 240 && heading < 300 ){
    digitalWrite(WPin, HIGH);
    digitalWrite(SPin, LOW);
    digitalWrite(EPin, LOW);
    digitalWrite(NPin, LOW);
  }
  //NorthhWest
  if (heading > 300 && heading < 330 ){
    digitalWrite(NPin, HIGH);
    digitalWrite(WPin, HIGH);
    digitalWrite(SPin, LOW);
    digitalWrite(EPin, LOW);
  }
  
}

void readCompass(){
   Wire.requestFrom(HMC6352SlaveAddress, 2); //get the two data bytes, MSB and LSB

  //"The heading output data will be the value in tenths of degrees
  //from zero to 3599 and provided in binary format over the two bytes."
  byte MSB = Wire.read();
  byte LSB = Wire.read();

  float headingSum = (MSB << 8) + LSB; //(MSB / LSB sum)
  headingInt = headingSum / 10; 

  Serial.print(headingInt);
  Serial.println(" degrees");
}

float calculateDirection (float lat1, float long1, float lat2, float long2) {
  // returns initial course in degrees (North=0, West=270) from
	// position 1 to position 2, both specified as signed decimal-degrees
	// latitude and longitude.
  float dlon = radians(long2-long1);
  lat1 = radians(lat1);
  lat2 = radians(lat2);
  float a1 = sin(dlon) * cos(lat2);
  float a2 = sin(lat1) * cos(lat2) * cos(dlon);
  a2 = cos(lat1) * sin(lat2) - a2;
  a2 = atan2(a1, a2);
  if (a2 < 0.0) {
  	a2 += TWO_PI;
  }
  return degrees(a2);
}