Use of “iPhone”, “iPad”, etc. in iOS apps An iOS app we're making has features which will work only with certain Apple devices. Can we mention them specifically as “iPhone”, “iPad”, etc. or should we use generic terms, e.g. “compatible smartphone”, “compatible tablet”? This would be text in the app itself, e.g. a button labelled “Connect to Your iPad”.

The guidelines indicate separate rules for publications depending on the target, e.g. “iPhone®” within the US, but “iPhone” with a separate credit section outside of the US. But does an app count as a publication? We can't really guarantee someone outside the US will not download an app targeted to the US, or vice versa.

I guess precedence would help here. Is anyone familiar with an iOS app which uses “iPhone”, “iPad”, etc. liberally in the app itself?
You should be OK. Apple guideline 3.3 states 


  Guideline 3.3: Apps with names, descriptions, screenshots, or previews not relevant to the content and functionality of the App will be rejected.


If your app requires a specific device to function be sure to mention that in the comments when you submit it for review. 

The main thing you can't do is mention a different platform:


  Guideline 3.1: Apps or metadata that mentions the name of any other mobile platform will be rejected.


You can really help yourself by clearly indicating why you used the device name in the comments. I always add comments during app submissions and I believe it's helped prevent a few rejections for more info.