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.
spacedesk - spacedesk expands the Windows desktop computer screen to other computers over the local area...
Astropad - Astropad is a free form drawing tool designed from the ground up to take advantages of the features offered by an iPad.
Air Display - Air Display allows extra screens to extend the display size of a Mac desktop. The company behind the product is Avatron Software, which was founded in 2008. Read more about Air Display.
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.
TwomonUSB - You can create dual monitors quickly and easily using a USB.