I'm retrieving my iPod Touch's device id in my app so I can run the full version on my device without purchasing it (this is let me retain me the capability to check both purchased and non-purchased versions).
The retrieval works fine on my device under the developer's license, but my question is, will there be a problem with permissions or anything once it's running on someone else device after having been downloaded from the app store?
You can access the UDID, but they've indicated that that access is deprecated, so may disappear at some future point
http://ios5source.com/2011/08/19/udid-deprecated-who-is-screwed/