Best way to target a universal app to only retina iPhones and all iPads?

I would like to restrict a universal app to be installable on all iPads and some iPhones (those with retina screens).  Is there an easy/good/approved way of doing this?

After doing a bit of research it looks like I can target the iPhones I want by adding a required device capability of front facing camera.  However doing this would remove iPad 1 from the list of supported devices.

After doing a bit more research it appears that in iOS you can modify a info.plist key so that it only applies to certain devices.  So the following requires a front facing camera on iPhones only:

<key>UIRequiredDeviceCapabilities~iphone</key>

                              <array>

                                        <string>front-facing-camera</string>

                              </array>

Will this work for an AIR iOS project?  Everything seems to compile ok with no warnings so I'd like to believe it will work.  Has anyone tried it and know either way?

There may be an issue with requiring a device capability and not using it explicitly, but some developers appear to have successfully used this method to target apps to specific phones and have their apps approved by Apple.