Piwik has a great feature to track details of a product page visited:
This also works when these informations are not within
or if the same product is available on different urls*
It's done by using "setEcommerceView" feature
Already tracking these data, it would be awesome to make it also usable - e.g. within goal definition.
Having this, one could set up really interesting goals like:
*In several shop system products are accessible on different urls.
e.g. in Magneto these are:
may look like this (UI):