You could do something like this with eCart by creating the listing of items on a page, then applying an add to cart button for each of them.
You would then need to combine all of the forms and remove all but the final add to cart button.
Finally you would need to update the triggers that are used for the add to cart server behaviors on the page, they will need to be based on the posted quantity being greater than 0.
This technique is a little custom and would only apply to static product listings. You would need to get into the code a little to get it to work this way.