Unity Remote 5, allows you to use an iOS device to view and test your game live, right inside the Unity Editor without having to build your project. Unity Remote 5 makes your iOS device act as remote control. It streams touch, MFi gamepad, Siri remote (on Apple TV) accelerometer, gyroscope, webcam and screen orientation events back to Unity Editor. This is useful for rapid development when you dont want to compile and deploy your project to iOS device for each change and prefer to use the Unity Editor Game window instead. Unity Remote is compatible with any Unity version newer than 5.0, but some features require Unity 5.4 or above.
Full documentation is available on https://docs.unity3d.com/Manual/UnityRemote5.html