If your iPad is just sitting on your desk not being used while you work on your Mac why not use it as a second display? Macs have supported multiple displays ever since the Mac II (introduced in 1987). I gotta admit that when I first heard about the Air Display App I wasn't all that excited. I just didn't think the performance would be good enough since it connects via WiFi. However, I just got around to testing it yesterday via my 802.11n WiFi network and I was really taken back by how well it works! Wow! I downloaded and installed the Mac client. After a reboot and launching the App on my iPad I had the choice of using it as a second display to my MacBook Pro. The next thing you know I was dragging panels over to it from Photoshop CS5. I was dragging Safari browser windows over to it and most importantly I was using it to view images in Adobe Photoshop Lightroom 3 since Lightroom has Second Display support! I was doing this all wirelessly without any hiccups. It just worked. I was also impressed that it even supported the rotation of the iPad display in both portrait and landscape on the fly. Again, it just worked. No lagging to speak of. No issues.
The icing on the cake…
Since your iPad is a touch screen, using the iPad as a second display for your Mac also makes it a touch screen Mac display. This means that you can tap on whatever is on that display to click the mouse on that spot or to make selections. You can drag things around and basically use your finger as the mouse. Now while I've only tried this App on the iPad it was recently updated to work on iPhones and the iPod touch as well. Frankly, with such a small display size (iPhone) I couldn't really see using it on anything smaller than the iPad. Also the only other thing that you have to keep in mind is that although the connection from your Mac to your Air Display iPad is wireless via WiFi, the iPad'd display is going to be on the whole time. So you're most likely going to want to plug in your iPad to AC/USB power as to not suck down the battery. Otherwise, if you're an iPad using Mac user this is one of those must have Apps!
You can get Air Display here from the 
Air Display
Air Display turns your iPad, iPhone or iPod touch into a second display (wireless) for your Mac
- Avatron Software, Inc.
- Get on App Store
- $9.99
All info was collected on 29th June, 2010 when the app was reviewed.
About Terry White
Terry is the co-author of The Best Selling "The iPhone Book" 1st, 2nd, 3rd and 4th editions. He has been active in the industry for over 25 years and is the founder and president of MacGroup-Detroit, Inc., Michigan's largest Macintosh Users Group, host of the Adobe Creative Suite Podcast and a technology writer - Terry White Tech Blog.
Sounds really nice. Changing the subject, have you seen LucyPhone.com? No more waiting on hold! Sweet, free service.
David Leatherwood
I was disappointed to learn that it doesn’t support PowerPC machines, of course neither does another alternative, iDisplay. Which unfortunately I discovered a bit too late.
Any way to apply this app to make it work as a tether device for my camera???
Not without using a Mac in the middle of the process.
If it can be used as a second display with LR3, how well would it perform as a “poor-man’s” cintique? i.e. touch-pad display for basic editing via LR…
Thanks! I’ve been thinking of getting this app, your review/comments prompted me to go out and snag it.
I downloaded but could not get it to work!
I have been using this for a while now, and it is really cool and useful. Frees up real estate on the Mac in Photoshop, or as a remote-control in Logic Pro. I’d like to know if the iPad could be used as a tablet device for selections in PS or is there another app that could do this?
Does anyone know of a similar solution that would allow sharing screens between two macs instead of a mac+ipad? I would like to be able to drag one mac’s window over to the other’s screen.
Thanks.