Documentation

/**
 * Returns the exposed filter widgets for a view.
 *
 * @param mixed $view
 *  Either a string with the name of the view or an object of the view
 * @param string $display_id
 *  An optional string with the name of the display for the view.
 *
 * @return string
 *  The themed exposed filter form.
 */
function embed_views_exposed_form($view, $display_id = '') {
To figure out the id of a display, look under Other, in the view edit page for the particular view that will be embedded, for Machine Name: what ever this name is is what should be used for the $display_id variable.

Usage

Simple version of code to embed an exposed filter.
  print embed_views_exposed_form('test', 'embed_1');
Advanced version of code to embed an exposed filter when embedding a view without views_embed_view().
  $view = views_get_view('test');
  $view->set_display('embed');
  print embed_views_exposed_form($view);

  ... some other code ...

  $view->destroy();