Is it possible to have an interface which can only be implemented by subclasses of a certain class, and be able to use properties/methods of that super class in the interface? For example in my Android app, a few activities do the same things in onCreate etc, but it seems restrictive to write an Activity subclass and have them all inherit it

Try CompositeAndroid library... It allows making plugins based on lifecycle events, and then plug them into multiple activities. You can also make more than one for one activity...