We've been fans of Avatron's Air Display for quite awhile. The iOS app lets you turn your iPhone or iPad into an additional monitor for your Apple desktop or notebook -- a productivity guru's dream come true. However, the app's US$9.99 price might have prevented would-be customers from jumping on board, because they're never seen it in action. Air Display Free changes that by offering a no-cost, ad-supported experience to show potential buyers how it works.
The free version also includes a handy introduction tutorial that lays out the benefits of using your iOS device as a second (or third) monitor. The ads pop up every few minutes at first, but after several hours of use, an ad will remain on a small portion of the screen until either the app is upgraded to the paid version or the connection to your computer is closed.