Deal Finder

Say I am shopping for a desktop computer. I go to different websites and sign up on their email newsletters for deals and all that. Then when I have bought my desktop, I am still spammed by these retailers for stuff that no longer want. I should have a personal agent (web based?) to whom I can say that I am shopping for a desktop. This agent will go to different retailers to look for deals, sign up for newsletters (parse these for deals, etc.) and do all that for me. Whenever it sees something in the market that might (lots of fun algorithms in figuring out what "might" could mean!) interest me, it will notify me (via email?). Once I have completed my purchase the agent can then unsubscribe from mailing lists of different retailers and even if it cant, it can directly junk all these emails. It can also stop crawling the web for deals on that particular item.