Calculate compass bearing / heading to location in Android

I want to display an arrow at my location on a google map view that displays my direction relative to a destination location (instead of north).

a) I have calculated north using the sensor values from the magnetometer and accelerometer. I know this is correct because it lines up with the compass used on the Google Map view.

b) I have calculated the initial bearing from my location to the destination location by using myLocation.bearingTo(destLocation);

I'm missing the last step; from these two values (a & b) what formula do I use to get the direction in which the phone is pointing relative to the destination location?

Appreciate any help for an addled mind!