Astropad - Astropad is a free form drawing tool designed from the ground up to take advantages of the features offered by an iPad.
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.
Paper by WeTransfer - A collection of creative prompts
Milanote - Milanote is a note taking app for creative work.
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.
ScribbleBoard - iOS8 Keyboard for hand drawing your messages