Drag and Drop to Add Products to Cart?

Hello All, I have googled and searched for days – high and low in the attempt to find a solution to my clients needs. And I can’t believe that I can not find one single solution.
The concept is (supposedly) simple. A reinvention/modification of the Shopping process.

Products are displayed in a Box or Panel, and users should be able to drag products and drop them in their Shopping Cart.

Having a front end, easy to use Drag and Drop interface to Add/Remove products to the Cart. There must be a reason why no one has done anything like this?
As a developer I would be thrilled to hear of anyone who has any leads into this area.

Thanks for your consideration.

Edward