iDisplay lets you use iOS or Android devices as touch-enabled secondary displays. It gives you more screen space for everything you have to keep your eye on.
Features:
Mirror your main display to your iOS or Android device. This comes in handy when you need to share your desktop with your audience. Keep in mind that iDisplay allows you to connect up to 36 iOS devices to one Mac!
Single-window mode: use iDisplay for one application of your choice. Quickly move selected apps from list of your favorite apps to iDisplay with one click!
Zoom and pan your desktop right on secondary display.
Easily switch between portrait and landscape screen orientations. Simply rotate your device and it will adjust automatically.
Customize display settings for each device you use as your secondary display. iDisplay will remember your preferences.
What’s new in version 3.3.0
Updated on Jan 17 2018
Version 3.3.0:
Release notes were unavailable when this listing was updated.
Really wish this worked with USB and Android devices. Sigh... That said, it DOES work with Android devices over WiFi, but it's a bit laggy due to those constraints. If you need some extra space to monitor something and you don't mind the lag, this is OK.