Custom feed element

I was wondering how exactly I would use a custom feed element.
In my case it’s a an element <media:embedcode>, used in the <item> element. (Not in <media:group>) (ie: hoping to get and use the foobarbaz out of <media:embedcode>foobarbaz</media:embedcode>)

I’ve managed to find out how to make extra template tags for WP-O-Matic, but now to assign the contents of the element. I was thinking along the lines of $item->get_item_tags('http://search.yahoo.com/mrss/', 'embedcode'), but that does not seem to work. (?)

http://ww.wp.xz.cn/extend/plugins/wp-o-matic/