Meet the Luna Display dongle: a clever tool that lets you use your iPad Pro as a second display for your Mac. Available in Mini DisplayPort and USB-C versions, Luna can be set up to work over your WiFi network in seconds. When you launch it, you are running macOS on your tablet. You will be able to interact with your apps with keyboard, Apple Pencil, or simple touch gestures.
The above video shows how one can use this dongle to use an iPad Pro 12.9″ as a second display for a Mac Mini. Costs $79.99 at this time.[where to find it]