Lazy Web Request

I would like a meta-search of downloadable music for sale online. I would like to search the iTunes, Napster, MusicMatch, Rhapsody, and Walmart music catalogs for a particular artist, track, or album. The search results would do a price comparison when the same track was found on two different sites.

My initial research shows that only one or two of the sites listed make their artist lists public. Otherwise, to get this information you have to sign up and download their client application. In some cases, the catalog data may be available by using a packet sniffer to track the client communication with the server. In other cases the data is encrypted. To build the meta search service without the consent of the companies involved would likely require a hybrid screen scrape, packet sniff, and maybe even OCR approach.