From the Archives, i found this:
http://www.zen-cart.com/forum/showth...=stand+payment

I've been unsuccessful in trying to contact the owner of that site or the contributor. Is there any plan to have something like this in upcoming Zen releases? Would be great for ebay integration and things to allow customers to use their credit card to checkout.

You can see the example from that archived link here:
http://www.myvehicle.co.uk/index.php...e=adhocpayment