When you're building your product you have the option to add tracking codes to the "success" page - you can add Google & Yahoo code - so you can add some other tracking code if you wanted as well. However, you would have to implement the tracking code on your own website in order for this to work.
Maybe Google Analytics will do this for you, I don't know.
As far as something that is built-into the system here, I don't know that - but from the way that their instructions read, you can add 3rd party tracking codes to the product download page.
