Yesterday I had the chance to see an Android phone (the German G2) in action. Part of the demonstration was the scanning of a barcode and the display of what it is and how much it costs in various shops.
Based upon this I had an idea. I added it to my ideas page, see there for more info. In short: scan some product and get similar no-name products (if it is a branded one), or the branded product this is based upon (if it is a no-name product).