There are two bits, first whatever website you use has to take an EAN (UPN) as an input, and then you need to parse the output.

Certainly not rocket science, but my hacky Amazon code was segfaulting so I removed it so the rest of the app was more usable.

barcodepedia is an option, or Amazon (possibly through the webservices api to make the parsing easier), and there are more.

If people are interested in doing some work here, either in writing EAN/UPC lookup tools, or apps that will use the barcodes (perhaps using the previously mentioned tools) then please pipe up. We need to work out an api to register and allow other plugins to use lookup services, etc. and also to give them, optionally, a window to do their thing in.