I've just added a plugin which lets you look up any result on Google. It will be expanded with more search engines later.

It should show up in extras-devel within a couple of minutes. Just search for mbarcode and install mbarcode-plugin-webrequest. It will be included by default in the next version of mbarcode.

How do you suggest the user should select the search engine? Should it be a button saying "Look up with search engine" which opens a dialog where one could select Google, Amazon etc.?