Auto grab first image from post body

How rad would it be if this module could grab the first image from a post body, download a copy locally and map that to the filefield. Drupal Feeds would be unstoppable.

Here is the string function I'm using to process the $content variable in the theme layer. This is nice, but I don't have a local copy and I can't run it through imagecache, etc.

function mymodule_catch_image($string) {
  $first_img = '';
  $output= preg_match_all('/<img.+src=[\'"]([^\'"]+)[\'"].*>/i', $string, $matches);
  $first_img = $matches[1][0];

  if(empty($first_img)){ //Defines a default image
    $first_img = "/images/default.jpg";
  }
  return $first_img;
}

I'd love to incorporate this into the module, as I've wanted to accomplish this forever. I'll just need some guidance.

I'm still on the DrupalCon high, so catch me while I'm inspired :)