I've got an existing iOS app, which still supports iOS 7, I would like to keep that for some time. But I would also love to have an Apple Watch app - is it possible that the app extension for WatchKit is iOS 8 and the parent iOS is iOS 7 or do I have to lift that to iOS 8 as well?

**EDIT:** 

I just uploaded my build to `Crashlytics` because I wanted to let users test the app before submitting to Apple, one user (running iOS 7) got the error `"The developer needs to upload a build that supports your device's architecture (armv7)."` Now I'm afraid that apps with the WatchKit extension don't run on older devices... Or does this have something to do with Crashlytics? Because in the Simulator it works without problem...