Use of “iPhone”, “iPad”, etc. in iOS apps
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.