Get the tracking spaces origin position and rotation

AlignToVrNode

using UnityEngine;
using UnityEngine.VR;

public class AlignToVrNode : MonoBehaviour
{
    public VRNode VrNode = VRNode.RightHand;
    
    void Awake()
    {
        //If VR isn't enabled, don't try to track this object
        if (VRSettings.enabled == false)
            Destroy(this);

        VrOrigin.SetVrHead(Camera.main.transform);
    }

    private void Update()
    {
        this.transform.position = VrOrigin.Position + UnityEngine.VR.InputTracking.GetLocalPosition(VrNode);
        this.transform.rotation = VrOrigin.Rotation * UnityEngine.VR.InputTracking.GetLocalRotation(VrNode);
    }
}

VrOrigin.cs

using UnityEngine;

/// <summary>
/// Determines the position and rotation of the VR spaces origin.
/// Works Best if VrOrigin.SetVrHead(Camera.main.transform); is called from Awake()
/// </summary>
public static class VrOrigin
{
    public static Vector3 Position
    {
        get
        {
            if (vrHead.parent == null)
            {
                return startLocalPosition;
            }
            else
            {
                updateOrigin();
                return _position;
            }
        }
    }
    private static Vector3 _position;

    public static Quaternion Rotation
    {
        get
        {
            if (vrHead.parent == null)
            {
                return startLocalRotation;
            }
            else
            {
                updateOrigin();
                return _rotation;
            }
        }
    }
    private static Quaternion _rotation;

    private static Vector3 startLocalPosition;
    private static Quaternion startLocalRotation;
    private static Transform vrHead;

    /// <summary>
    /// VrOrigin must be instanciated on Awake(), not in an Update(). It needs the initial localPosition before head tracking is applied to Camera.main
    /// </summary>
    static VrOrigin()
    {
        if (vrHead == null)
        {
            SetVrHead(Camera.main.transform);
        }
    }

    /// <summary> For the most accurate values, this function should be called in Awake() </summary>
    /// <param name="HeadNode">ie Camera.main.transform</param>
    public static void SetVrHead(Transform HeadNode)
    {
        vrHead = HeadNode;
        startLocalPosition = vrHead.localPosition;
        startLocalRotation = vrHead.localRotation;
    }

    private static void updateOrigin()
    {
        if (vrHead.parent.hasChanged) // only needs to be updated if the global position has moved. TODO: support grandparent, greatgrandparent, etc being moved
        {
            vrHead.parent.hasChanged = false;
            _position = startLocalPosition + vrHead.parent.position;
            _rotation = startLocalRotation * vrHead.parent.rotation; // TODO: work for all rotations, right now only works if the parent has 0 rotation
            Debug.Log("rotation updated to " + _rotation.eulerAngles);
        }
    }
}