If you have a store with physical inventory or just want to keep track of your priced collection of “X”, Inventory List may be the app for you. It has been featured by Apple as a “New apps we love”.
You can use Inventory List to track inventory across several locations (like shops) on several devices. A change on one device means a change on the others. Inventory can be categorized into groups and you can scan bar codes in the app.
The app is free to download but costs about 30 USD a year to use.