Air Display makes your iPad a Mac display

No, that's not Mac OS X running on an iPad. I'm not that much of a super-hacker. It's something very cool in its own right -- Air Display, an iPad app that turns your tablet into a second display for your Mac.

The $9.99 Air Display makes a great business travel tool. Many people use multi-monitor displays on their desktops in the office, but it's not exactly practical to drag an extra monitor around with your notebook computer -- until now. Run Air Display, prop your iPad up next to your notebook computer, and you now have a second display while you're on the road. The developers note that the 1024x768 resolution of the Air Display on iPad nearly doubles the size of a MacBook or Air 13" display.

I've been running Air Display as a little shelf for my open Skype and Adium IM windows. If you regularly use applications that have control palettes, like Microsoft Word, Apple Pages, or Adobe Photoshop or Illustrator, you can park the palettes on your iPad and keep the application open full-screen on your main display. Musicians can use Air Display as a control surface for Logic and Pro tools.

To use Air Display, you require two software components: First, download and install Air Display from the App Store, just as you would with any other app. When you start Air Display, it directs you back to the Air Display Web site, where you download a free desktop application for your Mac. The desktop app installs a Systems Preferences panel, a video driver, and a couple of other components.

With the desktop app and Air Display iPad app running, you can connect your iPad to your Mac over Wi-Fi and use it as a little extra monitor. Your Mac thinks the iPad is just another display. By opening the Displays panel in System Preferences on your Mac, you can change the virtual position of the iPad in relation to your main display, move the system menu bar to the iPad, and do anything else you'd normally do with a secondary display on your desktop.

But wait. There's more (as the TV commercials used to say).

You can use the iPad's touch interface to interact with desktop app windows that appear on the iPad. The interaction is limited: You can move windows around and resize them by dragging them with your finger, and tap to set the mouse focus and press buttons and drag scrollbars. Tapping and sliding on text selects the text. But the app doesn't seem to support the iPad two-finger gestures.

I've found Air Display to be pretty responsive. When you drag a window from place to place, the window stays under your finger or mouse cursor. Typing is realtime. On the other hand, I was unable to watch video in a browser window running on the iPad.

Air Display only works on a Wi-Fi network, and your Mac and iPad must be on the same network. It requires an Intel Mac running Mac OS X 10.6.3 Snow Leopard. The developers, Avatron Software, say they're working on a Windows version of the desktop software.

Mitch Wagner is a freelance technology journalist and social media strategist. Follow him on Twitter: @MitchWagner.