Use quaternion(s) to rotate the accelerator reading

I am using some code to move my player using the orientation of the phone. When the phone is face up, the player is not moving. Below is the code that I use to access the orientation.

 Vector3 dir = new Vector3(Input.acceleration.x, 0, Input.acceleration.y);

How would I go about rewriting this to check the orientation of the device when the script starts, in order to allow the player to position the device in a more natural way. I would like to generate an "adjusted" acceleration Vector3 that would replace the Input.acceleration references above.

I know that this would probably use Quaterion.FromToRotation, but all of my attempts at working with this have failed.