I just updated Tellico to use the latest version of the Amazon E-Commerce Service, version 4. The added capabilities of version 4 allow Tellico to do a proper UPC search now, and some additional item attributes are now exposed by Amazon.
What that really means is that UPC lookup by barcode is fully functional. I bought one of the modified Cue-Cat barcode readers, and I've been using it to test Tellico's search functions. If the UPC starts with "978" or "979", it gets converted to an ISBN and the proper book search is done. Otherwise, the UPC is used as the search item on Amazon. I've been able to scan DVDs and CDs successfully. Sweet!
I think I've got all the bugs ironed out, so if anyone wants to give it a spin, download the SVN trunk code from Novell Forge.
The trunk code is still a bit unstable, so back up your data first! You won't be able to open new data files with older versions of Tellico.