changing default accelerometer position

I am in the process of making an app that moves an object based upon the accelerometer and have been looking for a solution to my problem for a few days now. Basically I can move my object using my phone accelerometer however I have to have my phone stand upright for a default no movement position. I am looking for a way for the default value to be tilted to a more natural position. I am using C# and 3d project

I have done this so far with the following:

         Vector3 movement = new Vector3 (Input.acceleration.x, 0, -Input.acceleration.z);
         rigidbody.AddForce (movement * (speed +(count * 100)) * Time.deltaTime);

I have tried to add this

 movement = Quaternion.Euler(0, 0, -45) * movement;

to alter the default position but as yet no joy. Anyone shed some light on how I could move the axis as such so the 0 line is perhaps at a 45 degree angle.

Thanks in advance James