I've never used Simplepie before so I might be talking out my arse but couldn't you just edit the templates? Adding your url data right before the {ITEM_PERMALINK} tag? (e.g.
Code:
<a href="http://mydomain.tld/statisticsadress={ITEM_PERMALINK}">
)
I don't know if that's what you need or not but let me know what you need and I'm more than willing to try and help. (I just don't know your needs yet)
Also, if that is not what you're referring to you can use the post-processing functionality if the urls you're referring to are in the content of the items.
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