Launching Facetime from your app?

As a general rule, if you use undocumented API calls and apple catches you, they will reject your application. The reason is because they could change the API call that you are using in new IOS updates and thus would cause your application to crash or not work properly. You can try and submit using the undocumented API and hope that apple lets it through but as i said, you run the risk of Apple changing this api call or removing it completely from the OS in the future.

This is now documented and legal: https://developer.apple.com/library/ios/featuredarticles/iPhoneURLScheme_Reference/FacetimeLinks/FacetimeLinks.html#//apple_ref/doc/uid/TP40007899-CH2-SW1

My app got rejected for using FaceTime url. This is the part of response i got from Apple in resolution center.

We found the following non-public API/s in your app: Specifically, your app uses the FaceTime URL scheme, which is undocumented.

If you have defined methods in your source code with the same names as the above-mentioned APIs, we suggest altering your method names so that they no longer collide with Apple's private APIs to avoid your application being flagged in future submissions.

It was an update of a previous release. The first version got accepted without any problem. Now the update has been rejected due to the above mentioned reason. Seems i have to publish the app without the FaceTime thingy now.

Edit:

Its now legal to use FaceTime url in third party apps.