I've had the MiSubaru Android app since I got my Forester last year. It's there and it's of limited real "use". It does have a one click "Request Assistance" button that's meant to take you to their support team for recovery/breakdown/whatever. I've not used it so don't really know what happens. It lets you add reminders, add insurance info, car info, personal details, and has a button to "Send Mi Details" if you have an accident and need to share your info with the other party by email, which is sort of cool, but also something you can do by text or email yourself.
I haven't been in the app for an age, and tried it today, and it's refusing to load any of my details, my car details or reminder data, even though still shows my name in the main screen. Try to update anything and it hangs loading, or just displays a blank page looking for me to re-add my data again. So guess if I do need to Send Mi Details, i'd be quicker emailing them myself.
TLDR : The app doesn't really do much more than you can do in your phone addressbook and calendar. You're not missing anything by not having it.