With Unity Remote 5 you can use an Android device to view and test your game live right inside the Unity Editor 5.4 or later. Unity Remote 5 makes your Android device act as remote control. It streams touch accelerometer gyroscope webcam and screen orientation change events back to Unity Editor. This is useful for rapid development when you don't want to compile and deploy your project to Android device for each change and prefer to use the Unity Editor Game window instead.
Extended product documentation is available on Unity Manual: https://docs.unity3d.com/Manual/UnityRemote5.html

Unity Remote 4 still available at Unity Asset Store: https://www.assetstore.unity3d.com/en/#!/content/18106