Duet Display - With Duet Display, you can transform your iPhone or iPad into a second display to expand the screen space of your PC or Mac system.
Lunar.fyi - Control monitor brightness, adapt using the ambient light sensor, adjust volume, switch inputs and turn off displays without fiddling with clunky buttons.
Astropad - Astropad is a free form drawing tool designed from the ground up to take advantages of the features offered by an iPad.
iDisplay - iDisplay is an app that turns a mobile device into a secondary desktop monitor. The app currently supports iOS, Android, Windows and MacOS, and it lets users connect a desktop computer to a mobile device over WiFi. Read more about iDisplay.
DisplayBuddy - Control the real brightness of your monitors directly from your Mac - no need to touch the buttons on your Monitor.
spacedesk - spacedesk expands the Windows desktop computer screen to other computers over the local area...