You could create the url using the following:
// This shows us a search result with two colors and a brand
/products?f[0]=field_brand%3A51&f[1]=field_product%253Afield_color%3A14&f[2]=field_product%253Afield_color%3A41
/products? <-- that's the first part, will always be like this
f[0]= <-- that's the first facet, will likely only need one (which is zero here)
field_brand <-- that's the field name that we're faceting. Will likely be a color field or a brand field or a size field
%3A <-- that's the combining character... essentially "="
51 <-- that's the term_id that we're looking for in that field
%253A <-- that's the indicator that we have another facet
So ... some php might look like this:
<?php
foreach ($terms as $term) {
echo '<li><a href="/products?f[0]=field_something_cool%3A' . $term->tid . '">' . $term->name . '</a></li>';
}
?>
Wouldn't take much to turn that into a checkbox-configurable form box that uses "drupal_goto()" to send you to the search results.