Inside a warehouse there are all sorts of crates. You can imagine this idea in a harbor crammed with containers too. These boxes are identified by tags that are read by flying drones, via cameras and pattern recognition software. These drones hover around and maintain a list of everything that is on the warehouse and their locations, updating the inventory as these items are moved.

Initially I thought this was going to be a good way to find my glasses at home, but soon realize my cat wouldn't allow it.