MacOS Could Soon Use Your iPad As A Second Display
The next version of macOS could allow you to use your iPad as a second external display without any third party software or hardware.
The feature is codenamed 'Sidecar' and is being developed as part of the next major release of macOS which will be announced at this years WWDC in June.
Sidecar would allow a user to hover over the green maximize button on any Mac window, and using a drop-down select "send to iPad" the window in question would then be displayed full screen on the users iPad.
Apple Pencil support would also be included in this new feature allowing you to draw in mac apps using the Apple Pencil on iPad.