Answer to a question posed on my blog here: http://mikeschinkel.com/blog/restful-web-services-in-wordpress-plugin/#comment-225704

educontent-generator-url.php

<?php

class EduContent_Generator_Url {
  static $dir;

  static function on_load( $dir ) {
    self::$dir = $dir;
    add_filter( 'do_parse_request', array( __CLASS__, 'do_parse_request' ), 10, 3 );
  }
  static function do_parse_request( $continue, $wp, $query_vars ) {
    if ( preg_match( '#^/educontent/generator$#', $_SERVER['REQUEST_URI'] ) ) {
      require( self::$dir . '/admin/templates/tcpdf/samp/flashcards.php' );
      exit;
    }
    return $continue;
  }

}
EduContent_Generator_Url::on_load( dirname( __FILE__ ) );