Automated Checkout Systems need to be written for Bitcoin to...
Upon Checkout at an online merchant.... the system creates a unique new Bitcoin Receiving Address just for me, and just for this specific order.
Then, the system automatically records and attaches THAT Bitcoin Receiving Address, to THAT order, in the merchant's system.
Later, the system should be able to automatically detect the fact that the proper amount was received, on that address, for that specific order, and initiate shipment of the product...
The mybitcoin.com shopping cart interface (SCI) already has what you need.