One of my students have become an expert at this. It works in judicial states or easier to do it anyway. I agree with Financeexaminer - DO NOT PAY THESE PEOPLE UPFRONT. There are a lot of scams out there about stopping foreclosures.
However, there are many court cases already that show that if the lender commits some violations (and this can be as simple as foreclosing without being able to show that they own the note - which is a very common problem specially for lenders who bought packages of mortgages from the originators) or engaged in predatory lending (remember those 125% loan to value loans and no-doc mortgages?) that the foreclosure can be STOPPED, the loan balance of the borrower reduced or wiped out completely.
Here are the judicial states where this "thing" works:
Illinois, Florida, Wisconsin, Ohio, Indiana, New Mexico, Arkansas, Delaware, Iowa, Kansas, Kentucky, Massachusetts, Nebraska, New Jersey, New York, North Dakota, Oklahoma, Pennsylvania, South Dakota, Vermont