Detect if an Android device is a phone or a tablet

This works fine for me:

function isPhone(mc:MovieClip):Boolean{

                    var tabletMinimumInches:Number = 5;

                    return(Math.max( mc.stage.fullScreenWidth , mc.stage.fullScreenHeight ) / Capabilities.screenDPI < tabletMinimumInches);

}

Then I just call it with isPhone(this); from my main document class (that extends MovieClip). If iit returns true, it's a phone.

Look at the capabilities class:

http://help.adobe.com/en_US/air/reference/html/flash/system/Capabilities.html

From screenResolutionX and screenResolutionY you know the resolution of the device, and from screenDPI you know the dots per inch. Those two sets of values will tell you the size of the screen in inches.