A simple checkbox before the search button that allows you to make the search/filter criteria persistent so that the same filter is applied whenever you return to the product listing. Unchecking the checkbox would reset the filter to defaults. The current filter options would be stored for the next page load of the product list if the checkbox is checked and the Search button is clicked.
Would be useful for Categories and Manufactures as well, but especially Products.
Remember Filter Criteria ☑