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?