Unity editor script to find all assets that depend on the currently selected asset (i.e. assets that have serialized references to the selected asset). NOTE: Currently only works on OS X.

FindDependentAssets.cs

using UnityEngine;
using UnityEditor;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

public class FindDependentAssets
{
	[MenuItem("Assets/Find Dependent Assets")]
	public static void FindAssets()
	{
		UnityEngine.Object selectedObject = Selection.activeObject;
		string[] paths = FindFilesReferringToGUID(AssetDatabase.AssetPathToGUID(AssetDatabase.GetAssetPath(selectedObject)));
		for(int i = 0; i < paths.Length; i++)
		{
			paths[i] = paths[i].Replace(Application.dataPath, "Assets");
		}
		List<string> processedPaths = paths.Where(path => !path.Contains(".meta")).ToList();

		List<UnityEngine.Object> dependentAssets = new List<UnityEngine.Object>(processedPaths.Count);
		foreach(string path in processedPaths)
		{
			dependentAssets.Add(AssetDatabase.LoadMainAssetAtPath(path));
		}

		FindDependentAssetsWindow window = EditorWindow.GetWindowWithRect<FindDependentAssetsWindow>(new Rect(0, 0, 640, 480), true, "Dependent Assets");
		window.Setup(selectedObject, dependentAssets);
	}

	[MenuItem("Assets/Find Dependent Assets", true)]
	public static bool FindAssetsValidation()
	{
		return Application.platform == RuntimePlatform.OSXEditor && Selection.activeObject != null;
	}

	public static string[] FindFilesReferringToGUID(string assetGUID)
	{
		System.Diagnostics.ProcessStartInfo mdfindInfo = new System.Diagnostics.ProcessStartInfo();
		mdfindInfo.CreateNoWindow = true;
		mdfindInfo.RedirectStandardError = true;
		mdfindInfo.RedirectStandardOutput = true;
		mdfindInfo.UseShellExecute = false;
		mdfindInfo.FileName = "mdfind";
		
		System.Diagnostics.Process mdfindProcess = new System.Diagnostics.Process();
		mdfindInfo.Arguments = assetGUID + " -onlyin .";
		mdfindInfo.WorkingDirectory = Application.dataPath;
		
		mdfindProcess.StartInfo = mdfindInfo;
		mdfindProcess.Start();
		
		string stderr_str = mdfindProcess.StandardError.ReadToEnd();
		string stdout_str = mdfindProcess.StandardOutput.ReadToEnd();
		
		mdfindProcess.WaitForExit();
		mdfindProcess.Close();
		
		if(stderr_str.Trim().Length > 0)
		{
			throw new System.Exception("Error getting git hash: " + stderr_str);
		}

		stdout_str = stdout_str.Trim();
		string[] paths = stdout_str.Split(System.Environment.NewLine.ToCharArray());

		return paths;
	}
}