Apps for photographers

So I would like to talk about apps for photographers - not those apps for sharing photos on Social Media (Tumblr, EyeEm, 500px etc etc) nor those apps for using the in-phone camera (either for taking or for processing photos) but, rather, apps to be used alongside an external camera.
And in our case, we’re obviously talking about a Fujifilm-something.
My experience is with iPhone and the Apple Store but I'd welcome feedback from Android and Google Play users too.

It seems that, for me at least, my iPhone is an integral part of my every day carry - it's use has obviously gone beyond “just a phone” and carries a lot of critical information and apps (not just for photography) but, it seems, for my everyday existence....It's clearly an essential tool for many people.

I think there are a lot of very good photo apps out there; but sometimes it's hard to sort out the good from the bad....
Please don't just recommended the name of the app - but, rather,give us some idea of it's use.

I will start with the apps I currently have on my iPhone.
I'll also add whether the app is ’free’, ’in-app payment’ (download is free but afterwards certain features are  unavailable or there is advertising prior to payment) or, ’paid’. 
Also, I don’t see any point in listing the prices since every Apple store uses the local currency and so listing the prices in Israeli Shekels won't help too much.

Currently on my iPhone are the following apps:

Fuji Cam Remote (free) - for connecting my new XPro-2 to my phone via wifi. Once I figure out how to use the camera then I’ll connect to the app.

TPE The Photographer’s Ephemeris (paid) - a highly sophisticated and very well designed app for landscape photographer.
If you want a photo of a full solar eclipse rising over the peak of your local mountain, this app will give you exact location, time and date.
Definite learning curve to this app

Photo Transit (paid) companion app to TPE - digital field of view and shot planning app for landscape photos.

Portal/Fuji (free) a shortcut portal to get into our favourite forum. Occasionally gets “stuck”

F-Stop (in-app payment) by Jefro Studios. A simple calculator for working out DOP and Hyperlocal Distance. Can set profile for camera (XPro-1 is the best option)

Pocket Light Meter (in-app payment) by Nuwaste Studios. Uses the phone camera to measure light with adjustable Time, Aperture and ISO settings. Can also connect to an external Luxi light meter. 
No idea of it’s accuracy.

So that’s my collection; please comment and add your own recommendations.