The iPhone comes in such a simple form that you could think of it as the core brain of a larger system. If you need to go underwater, you can get a case for that. If you want to turn it into a satnav for your bike or stroller, you can do that, too (see below).
The iPhone accessory market is huge, and there is a gadget or gizmo for almost anything. Here are some of our favorite iPhone accessories, for the new iPhone X as well as for older iPhones.