find the heading between two geographic coordinates based on http://stackoverflow.com/questions/3809337/calculating-bearing-between-two-cllocationcoordinate2ds

gistfile1.m

// from: current location
float fLat = (currentLocation.coordinate.latitude / 180.0) * M_PI;
float fLng = (currentLocation.coordinate.longitude / 180.0) * M_PI;

// to: waypoint location
float tLat = (waypoint.locationLat / 180.0) * M_PI;
float tLng = (waypoint.locationLon / 180.0) * M_PI;

// calculate it!
float locationHeading = atan2(sin(tLng-fLng)*cos(tLat), cos(fLat)*sin(tLat)-sin(fLat)*cos(tLat)*cos(tLng-fLng));

// print it
NSLog(@"Heading from newLocation to waypoint: %f",locationHeading*180/M_PI);