RhoMobile needs to adopt a strategy on this.
Rhodes returns the UDID (Unique Device ID) for System.get_property("phone_id") on iOS.
However, as of iOS 5.0, this is deprecated. I think it is only on 5.1 where it will not return a value. The App Store hasn't been accepting apps that use UDID for some time:
A possible alternative is OpenUDID:
However, this might have some risk of apps being rejected from the app store, because it does create a unique ID for the device that can be shared across apps.
Apple's suggested solution is to use CFUUIDCreate. This creates a unique application-specific ID. However, if the application is deleted and then re-installed, then CFUUIDCreate will return a different ID. This may not be suitable for all uses of the previously-supported UDID.
That problem can be worked-around by using the KeyChain. Then it is possible to re-use an application-specific UUID if the app is re-installed. But if the user restores their device from backup, then a new ID will be created. So, the ID can survive a re-install, but not a restore of the device from backup.
In any case, this all happened months ago, and RhoMobile needs to decide what to do about it.
Yeah, this posting was actually an attempt to get input from RhoMobile on this issue. It appears as though the capability slipped through the cracks and, as you very well pointed out, a strategy needs to be formulated to address the deficiency.