Duet Display is an app (available on both Mac and Windows) and website that allows a user to extend the use of their Mac or Windows device by transforming it into a second display. This app makes it easier to multitask and add a second display to your workspace. It also helps with productivity by allowing you to move windows and apps between displays with a simple drag and drop. With the app, you can also mirror your device’s display, use it as a whiteboard, and enjoy full Retina resolution. The website also provides helpful tutorials and FAQs about using the app.
spacedesk
Air Display
iDisplay
Splashtop Wired XDisplay
TwomonUSB
Astropad
Displaypad
It works as long as the computer you are trying to extend and the Apple/Android device is connected to the same WiFi network. The downside is that it is not as smooth as the Duo Display (but iDisplay is wireless anyway).