A Unity Shader LOD Script.

using UnityEngine;
using System.Collections;

public class LOD : MonoBehaviour
{
    //distances where LOD transitions occur.
    public float[] lodLevels = new float[] { 1000f, 800f, 600f, 400f, 200f, 100f, 50f, 10f };

    //These are the builtin LOD values for Unity shaders.
    int[] shaderLOD = new int[] { 600, 500, 400, 300, 250, 200, 150, 100 };

    void Start ()
    {
        StartCoroutine ("UpdateLOD");
    }

    void SetLOD (int LOD)
    {
        foreach (var i in renderer.sharedMaterials) {
            i.shader.maximumLOD = shaderLOD[LOD];
        }
    }

    IEnumerator UpdateLOD ()
    {
        var period = Random.value;
        var cam = Camera.main.transform;
        float[] levels = new float[lodLevels.Length];
        int i = 0;
        foreach (var level in lodLevels) {
            levels[i++] = level * level;
        }
        while (true) {
            var distance = (transform.position - cam.position).sqrMagnitude;
            var LOD = levels.Length - 1;
            foreach (var level in levels) {
                if (distance > level) {
                    SetLOD (LOD);
                    break;
                }
                LOD--;
            }
            // make LOD checking non deterministic. avoids stampeding LOD calls?
            yield return new WaitForSeconds (period);
        }
    }
    
}