You name it I have tried it :)
I have come to the conclusion there is not much you can do for calcified stones, except pushing them out, but it will probably help with the softer ones. This does not mean when someone comes up with something new I would not try it.
I would think for the average person malic acid (apples, apple juice, apple cider vinegar)will be fine.
This is based on a lot of reading I have done in the last 4 years.