Shopping Cart in Digital Catalog
Have a digital catalog have a shopping cart to store the products you are purchasing so that you are not taken to check out on a merchant's website every time you want to purchase an item. The digital catalog shopping cart would allow the customer to add, remove and change quantity of a product. Then when they are done shopping through the digital catalog they would check out and then get taken to the merchant's secure shopping cart where all the products they added from the digital catalog would be. They can then add, remove or change quantity and then go through the check out process.
Mark Madson commented
This would allow you to continue to shop without jumping from the digital catalog to the website shopping cart. Great Idea.