The cart is not yet developed, it-s just an idea.
As for the Compatibility Mod, here is a temp link (still not completely ok):
http://www.dynamonline.com/xcart/customer/product.php?productid=16145&cat=263&page=1.
I think Storefront (
www.storefront.net) has a nice side mini cart, and Nexternal Solution's is even a nice choice, one of them features in-line minicart edit of quantities and coupon recognition.
However I still think the e-frame concept is doable. Seen it in many other web pages on the net.
Still looking.