According to the latest Apple WWDC, starting from ios 9 there should be a way to limit installing app only on 64 bit devices.
I searched in XCode for this option but could not find anything. Is this already possible and if yes, how can i enable it?
In Xcode, set the following values:
Build settings > Architectures
Build settings > Valid architectures
The app will then not be able to run on a device that does not support 64-bit code.