Apps manually installed in simulator crashes upon load
I had the same problem, but using Xamarin. In Visual Studio I solved it by going to the iOS project properties and under "iOS Build" I changed the "Supported architectures" from "i386" to "i386 + x86_64".
Hopefully you can adapt that to XCode.
I encountered this problem in Xcode 6 when using the .app file in directory "Release-iphoneos" instead of "Release-iphonesimulator". There are multiple versions of this file, and you need to change the path in your install command to point to the correct one.
If this .app file was sent to you by someone/something else, it may be a copy from the wrong directory (not built for a simulator)
This can happen if you use the wrong sdk. If the project is built using the physical device sdk it crashes on start up when you try to open it on the simulator.
If you are building it from the command line with xcrun xcodebuild check thet the sdk is "iphonesimulator" not "iphoneos"
e.g xcrun xcodebuild -scheme <yourScheme> -configuration Debug -project <yourProject>.xcodeproj -sdk iphonesimulator build