Keep track of new songs you want to buy

The problem:
When lisening to music on the way home - in the car, the bus, the bike or where ever you might have some sort of personal radio-music device. Often when i listen to the radio i hear tracks I'd really like to buy - but since i'm busy doing other stuff than writing down the artist name, album and track name/number i never get around to buying the cd's.

The solution:
A bluetooth or other wireless or USB-enabled device which records the digital-id for each number i'm listening to. Alternatively it only records the id's when i push a button on the device.

I'm seeing this device as a USB-key. This is because more and more car-radios has USB ports, and because you can install programs directly to the usb key.

Uppon accessing a computer, the digital-id's can be transformed into a download list, or a list of the cd's for me to buy in an online store.

There is actually two products in this idea. 1. the usb-key (or just the program) and 2. the online store which has a record of the digital-id's

Background:
All tracks played today has a digital signatur. (RDS)

I've been looking into this - and it turns out that the RDS-forum has an article on the underlying technology required.
http://www.rds.org.uk/rds98/rds98.htm

RT+ will allow the radio receiver to "understand" the broadcast Radiotext. Understanding means, the radio station can tell the receiver,
that Madonna is an "artiste" Material Girl is the "title", but also
that 0800123456 is the "hotline phone number" and 08002132123 is the "sms number to purchase the title" and
that Andrew is arriving is an "alarm" and listener can get more info at either 0800-212122 or www.hurricane.org or at another FM frequency
The receiver will be able to act accordingly. It may display Title and Artiste nicely, and if it has a built-in back-channel (if it is a phone) the user might call the hotline with one click or the user can get more information from a web-site or from a hotline or even switch to another frequency.

The examples given here are somewhat standard for what you can expect i guess - but I'm still hoping to see this implementet in phones (as they write), Ipods, USB-keys and laptops.

When talking about USB-keys, i can see this together with the "central usbkey-hub" idea, previously written here: http://imaginatory.blogspot.com/2006/12/central-usbmemmory-readers-in-house.html