Unioncy is described as 'automated personal inventory that makes it easy to keep a record of your things and all of their associated information' and is an website in the Home & Family category. There are four alternatives to Unioncy, not only websites but also apps for a variety of platforms, including Mac, iPhone, iPad and Android. The best alternative is Delicious Library. It's not free, so if you're looking for a free alternative, you could try HomeZada or Simple-Inventory.
Catalog your books, movies, music, software, toys, tools, electronics, & video games in a nice interface. Import all your stuff onto your digital shelves using your Mac’s iSight webcam, our wireless barcode scanner, or your keyboard.