In 2015, I created an iOS app for Tesla so that Apple Watch users could control their Teslas from their watch. Since then, a large percentage of Tesla owners have started using my Remote app for their iPhones as well since it connects faster, exposes more car stats, keeps a location history, shows charging information from your last session, and has less restrictions when using Summon/HomeLink (no need to be near the car and no need to hold down the button). There's also Siri Shortcuts support so that you can do things like open your trunk by talking to Siri, combine commands in the Shortcuts app, and even summon your car by talking to your watch (see video:

I'm starting this new forum thread to answer all questions, bug reports, UI suggestions, and feature requests for the app. The app currently works for the Model S, 3 & X.
Download link:
http://itunes.apple.com/app/id991623777?mt=8&at=11l4Ui
Comments
"Be nice to park the car in visual range of the charger and be able to check the app to see when it's free, for example." => As Elon would say: you won't care. because the car can see it, together with live info from the supercharger and will park and charge itself without you g-having to worry about that. :-)
1. What data do you gather from the app back to your servers, and what do you do with it?
2. Is the password stored on the device, and if so what security measures do you take with it?
3. How are session identifiers (to communicate with Tesla) stored and protected?
Beyond a quick test of the app, I haven't had it/used it since it came out due to not knowing the answers to the above, so I appreciate that you put up this thread.
Love your app. Thanks
2. The password is stored in your device's Apple keychain for the sake of refreshing the 90-day expiring access token, and being able to use the keyless start with just TouchID. It is stored nowhere else. I take security and privacy very seriously. Even the username, tokens, and internal car IDs are encrypted and stored in the Apple Keychain and not stored in plaintext anywhere. When you log out of the app, all that information is wiped from your keychain. If you change your password, the current login session would be invalidated and then the app wouldn't be able to login using the stored password. So if you lose your device, you can remotely log someone off the app. If someone has your device but not the passcode, then they can't access your device's Apple keychain.
3. The access token is stored in the same secured fashion as your username and password and car IDs. I treat the access token like it were a username and password, because the access token gives anyone the power to unlock and locate that Tesla.
It would be nice to apply software updates to the car remotely, but I suspect that is simply impossible from Tesla's end right now.
Loved your book. You are a true American success story.
Also, this app gives you a lot more information about and control of your car than Tesla's app. I still like Tesla's app for its simplicity and visual effects, so I use both apps in different situations.
@redacted Thanks. There's two more security measures that I forgot to mention:
1. If you delete your app without first signing off, the username/password will still be in your Apple Keychain because the app never got a chance to erase it. However, if anyone tries to install the app again and use it, it will automatically delete that information from the Apple Keychain when the app first starts up. Of course, if you wipe your phone manually or remotely through iCloud, it will also erase the data in the Apple Keychain.
2. There's a "no commands" mode in the app or what I like to call "kids mode". If you login with that mode turned on, the app will be unable to issue any commands. Under this mode, the app is in a "get information only" mode where users can see the stats for your car but unable to control it without knowing your password to turn off the "no commands" mode. This is useful if you want to install the app for your family members to monitor your location without giving them the ability to screw something up like unlock your doors while you're parked on the street. And of course if you ever need to log them out remotely, you can reset the password. Or if you turn off mobile access in the car, then they will be unable to see your car stats until it is turned back on.
@regoapps - I love your app and use it regularly. My only request is to tweak the UI on the iPad so more info is shown at the same time. There is a ton of screen real estate available but the app crams everything into the three rectangles and overlays some it. Thanks for reaching out.
I'd love to see Remote S have a widget, as simple UI as Tesla app, and force touch on the icon, e.g. Toggles for HVAC, lock, keyless start (with touchid confirmation ;-))