Part of convert.c in the i-Glasses SDK. Note that "raw" should be called "cooked". An emulator needs to reverse this math.

CONVERT.C

void rawToEulerInt(long rawMagneticX,long rawMagneticY,long rawMagneticZ,
                   long rawGravimetricX,long rawGravimetricY,
                   long * eulerYaw,long * eulerPitch,long * eulerRoll) {
vec3 rotMagnetic;
vec2 linGravimetric;
vec2 normRotMag;
sinCos pitch,roll;

#ifdef USE_FILTERS
  if (!madeFilters) {
    if (!initFIR(&fx,3)) return;
    if (!initFIR(&fy,3)) return;
    if (!initFIR(&fz,3)) return;
    if (!initFIR(&f1,6)) return;
    if (!initFIR(&f2,6)) return;
    madeFilters = 1;
  } // if

  rawMagneticX = filterFIR(&fx,rawMagneticX);
  rawMagneticY = filterFIR(&fy,rawMagneticY);
  rawMagneticZ = filterFIR(&fz,rawMagneticZ);

  linGravimetric.x = filterFIR(&f1,MUL(rawGravimetricX,RAD180DEG));
  linGravimetric.y = filterFIR(&f2,MUL(rawGravimetricY,RAD180DEG));
#else
  linGravimetric.x = MUL(rawGravimetricX,RAD180DEG);
  linGravimetric.y = MUL(rawGravimetricY,RAD180DEG);
#endif

  sincos(&pitch,linGravimetric.x);
  sincos(&roll,linGravimetric.y);

// Inversely transform the magnetic vector back into definition space.
// This allows an easy computation of yaw by looking at the projection
// of the magnetic vector in the x-z plane, which is the plane of the
// earth.

// Perform a rotation about x: Pitch
  rotMagnetic.y = MUL(pitch.cos,rawMagneticY) - MUL(pitch.sin,rawMagneticZ);
  rotMagnetic.z = MUL(pitch.sin,rawMagneticY) + MUL(pitch.cos,rawMagneticZ);

// Perform a rotation about z: Roll. We only need x, so y isn't transformed.
  rotMagnetic.x = MUL(roll.cos,rawMagneticX) - MUL(roll.sin,rotMagnetic.y);

  *eulerYaw   = TODEGREES(getatan2(rotMagnetic.z,rotMagnetic.x));
  *eulerPitch = TODEGREES(linGravimetric.x);
  *eulerRoll  = TODEGREES(linGravimetric.y);

} // rawToEulerInt

Magnetic vector = (cos yaw, 0, sin yaw) into the eulerYaw equation should give back eulerYaw. Antirotate around roll then antirotate around pitch, so CONVERT.C rotates correctly. CONVERT.C assumes magnetic vector is relative to pitch/roll, so antirotating will give that.