I just found the apps twomonusb and twomonair on the app store. They should make it possible to us an ipad (and with the air version also iphone) as a extra monitor for a pc.

Has anyone tried this for flight sim use?

I was thinking that maybe I could hook up my ipad via the usb software and then have a panel-builder screen running on it for my instruments.... But before I invest in panel-builder and twomon vs investing in a dedicated ipad instrument app (which is probably less versatile then panel builder) I would like to hear if anybody has experience with such a setup?

That app looks awesome. Too bad it is split between two different apps. I might try out the air this week, see how it works.