I am subscribed to the Amazon Hip Hop Music RSS feed which provides information about available hip hop CDs on sale at Amazon. I was just thinking that it'd be really cool if once a CD I liked showed up in my RSS feed I could just click a [Buy This] button and initiate the process of purchasing the CD. Combining this with Amazon's one click shopping it's conceivable that this could be done in a single click.

At the minimum to implement something like this you'd need an annotation in the RSS feed that contained the end point for the aggregator to submit the purchase information securely and a specified format for what the submitted purchase information should look like. In the case of Amazon, it might just be a cookie while for others it might be the all the required information like credit card number and shipping address.

Now that would definitely be cool. A subscription to a list of things I might be interested in buying and the ability to buy one of them when something caught my eye.