It is possible to test multiple IOS devices with OSX Server and XCode Server
https://developer.apple.com/videos/wwdc/2014/
Continuous Integration with Xcode 6
I hope I have understood the problem correctly.
The Problem with test multiple IOS devices is. That instruments can run only one device at a time.
With XCode Server it is possible to run more then one device at the same time.
https://developer.apple.com/library/ios/documentation/IDEs/Conceptual/xcode_guide-continuous_integration/000-About_Continuous_Integration/about_continuous_integration.html#//apple_ref/doc/uid/TP40013292
https://developer.apple.com/library/ios/documentation/IDEs/Conceptual/xcode_guide-continuous_integration/ConfigureBots/ConfigureBots.html#//apple_ref/doc/uid/TP40013292-CH9-SW1
Has anyone tried this?
Can Appium handle multiple sessions out of the box or Appium changes are required?