I stumbled across this way cool app for iOS devices that I just had to cover this week. The app is called Air Display, published by Avatron Software, and it does something really cool: It turns your iPad, iPhone or iPod Touch into an extension of your OS X or Windows desktop, wirelessly!

You install the iOS app from the iTunes App Store (£6.99) and then the OS X 10.5.8, OS X 10.6+ or Windows application.

Note that at present there's a problem with the built-in video drivers on certain 2008 and 2009 Macs running OS X Lion. At the bottom of the Air Display home page there's a list of the machines that, at least for now, don't work with Air Display and OS X 10.7+.

When you launch the OS X app it places an icon in the menu bar while the Windows version places an icon in the system tray. In either case, when you click on the icon you get a list of the devices on your local network running the Air Display iOS client software as discovered by Apple's Bonjour service. If, for whatever reason, the client isn't "visible" you can also enter its IP address to get connected.

If you aren't familiar with Bonjour, Wikipedia explains it thusly: "Bonjour is Apple Inc.'s trade name for its implementation of Zeroconf, a service discovery protocol. Bonjour locates devices such as printers, other computers, and the services that those devices offer on a local network using multicast Domain Name System service records.

"The software comes built-in with Apple's Mac OS X operating system and iOS for iPhone, iPod [Touch], and iPad. Bonjour can be installed onto computers running Microsoft Windows operating systems. Bonjour components may also be included within other software such as iTunes. This happens without the user being able to deselect the software and as such, can be considered bloatware in some instances."

Aside: I think IT professionals should band together in a "No Bloat" campaign to get not only Apple but also Microsoft and every one of their OEMs to stop padding their products with tons of crap only a complete noob would consider in any way interesting. But I digress ...

Here's the thing about Air Display: Overall, it works amazingly well! Depending on bandwidth availability, the iDevice's display is excellent and, while you can move the mouse cursor from the host screen to the iDevice, you can also touch the iPad or whatever you use and control the cursor directly with your finger (though those of us with big banana-like fingers may have some precision issues).

Note that I wrote "overall" -- there appears to be a few minor problems with the Windows implementation. For example, I rearranged the displays and moved my iPad from the default right of the main display to the left and wound up with a blank screen on my iPad. After a small amount of faffing around (which involved enabling and disabling displays and restarting the host and client components) I got the iPad display where I wanted it.

Bottom line: Air Display is a very good idea and very useful. I love being able to display social networking apps and monitoring utilities from either platform on my iPad and I only wish it was possible to be able to connect simultaneously to multiple hosts and switch between them.