If you are using a Windows PC and want to extend the desktop work area without buying additional hardware with help of your existing Android or iOS devices like mobile and tablets then Spacedesk is the tool for you.
Spacedesk is a free software that lets you extend your Windows PC display wirelessly onto your Android or iOS devices.
It has two software components. Spacedesk driver or server that installs on your main Windows PC to which you want to extend your display. A client software that you will install from either Google Play store or iOS App store on your respective device.
Only requirement for this setup to work is that all these devices are to be on same WiFi network.
Just make sure the Spacedesk software is running on PC and fire up the app on the respective devices. The app would autodetect the server on Windows PC and would have an option to connect. Just click on the connect and voila now you have extended your PC display to your device.
Good thing is that this works with multiple devices at once.
Below is my setup on which I have tested and it works just fine.
You can reorder your screens in the Windows Display settings so that you can move your mouse to respective screen.
You can also use the touch on your devices if you do not want to you use the mouse. You have options to disable or enable touch.
It is very easy to setup and all this setup can be done within 5 minutes.The software is still in Beta but works without any hiccups.
For additional settings or help you can visit their documentation which is very good.
Download Spacedesk from here - https://spacedesk.net/##box_434
Read their documentation here - https://spacedesk.net/user-manual/