The correct “WordPress” way of doing it would be to use the_widget template tag to display widgets anywhere you want.
so in you case you would something like this:
$instance['account'] = 'account name'; //Ustream channel name
$instance['online'] = 'http://www.online_image.URL';
$instance['offline'] = 'http://www.offline_image.URL';
the_widget('wp_ustream_status', $instance);