I haven't seen one yet... but I have thought about writing one myself. I have some VB6 code that I've been playing with migrating to VB.NET to do duplicate file finding based on hashes of the file contents.
I have thought of putting this into a WHS add-in specifically to do what you are asking for as I could use it myself.
Time, however, is always the problem, and I've not had the time to work on personal projects lately with my work schedule.
If I do come up with something, I'll be sure to post it here.
Ted