Drones can come in all sizes, as Parrot likes to demonstrate with its MiniDrones line of more diminutive gizmos. And now, it seems there’s a small army of them—on land, air and sea. Previous designs have been augmented in various ways to make this new batch of mini robots smarter, sleeker and more precise. I took a few for some testing and found them to be fun for as long as the battery could last.