gistfile1.java

public interface MyCallback {
    public void execute();
}

public class MyConcreteCallback implements Parcelable, MyCallback {
    public void execute() {
        doSomething();
    }
    // Parcelable stuff
}


public class MyClass {
    protected List<MyCallback> callbacks;

    public void onAction () {
        for(MyCallback callback : callbacks) callback.execute();
    }

    public void registerCallback(MyCallback cb) {callbacks.add(cb);}
}

public class MyAndroidClass extends MyClass implements Parcelable {
    // Parcelable stuff
}

public class SomeActivity {
    MyAndroidClass mac = new MyAndroidClass();

    mac.registerCallback(new MyConcreteCallback());
}