Sometimes you just need more work space on your Mac. You could appease this by buying a second monitor, but it may well be that you need this space while on traveling — a place where a second full-sized screen becomes much more cumbersome than helpful. The solution? Use your iPad.
Duet Display is a tethered second-screen option that lets you borrow your iPad's Retina display for your Mac. You can display anything you like on that second screen — including full-framerate video — and interact with that content directly on the iPad, as well.