Mountie - Mount a second screen (iPad/iPhone/tablet) to your MacBook
Luna Display - Hardware that turns the iPad into a wireless second display
SecondScreen - A communications hub for remote, hybrid, and in-office teams
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.
shiftscreen for iPad and iPhone - External display for your iPad/iPhone!
Mountie+ - Connect a second (or third) screen to your laptop