I’ve written earlier to explain that AIR doesn’t include a device identifier API because it doesn’t have a useable definition across platforms. (Also, it can be easily replaced for most use cases with a random identifier generated by the app.)
Now comes news that this capability is becoming even less implementable: Apple is deprecating their own UDID API. TechCrunch has the story at http://techcrunch.com/2011/08/19/apple-ios-5-phasing-out-udid/.
Math.random() is your friend.