More apps have gone to a pay system. They were previously free. Do not let that stop you from making a purchase. It is such a piddly amount in the big scheme of things.
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Having a Victron solar controller I really like and use their app.
Allstays is my go-to app when looking for places to stay, includes Walmarts, Cracker Barrel, Elks, Corp of Engineers, private, state, county, local and many more. I like their reviews. Once in a while I find something missing, but not often. Using Google Maps, zero in an area, and search for camping is very useful. I cannot figure out if Allstays is fee based or not. I have contributed a number of reviews and maybe getting it free. Worth paying a fee. Somehow connected to Camp & RV.
RV Life - this has just gone fee based, it really had good campground reviews, not sure it still holds true, they do have a trial peroid.
Certainly, an app connected to your credit/debit card(s) with notifications of all transactions turned on.
I use Sensor Push for all temperature monitoring. It works well to check refrigerator temps while driving.
Shopping such as Canadian Tire, Auto Zone, Menards, Home Depot etc.
The EscapeForum has an app, many like it, I am not one of them. I do have a shortcut on my phone that goes to this website. It does work better on a tablet, simply because of more real estate.
US Post Office - so you know exactly what is coming to your mailbox.
An app for your tow vehicle, if it has one.
Note taking - To Do List Management to replace those sticky notes. I use Notes, built into Apple products but I live and die with the Microsoft Product called One Note.
Translate if you visit foreign countries.
Weather - I use Accuweather but you need to set it up properly. It should be configured allowing Location Access, Default Location = Current Location, and the Notifications/Alerts turned on that you wish. Accweather has an option called Government Alerts.
Insurance app - my insurance cards are only provided in a digital format. What an improvement, used to get one every six months. What is current? Not a problem with the app.
Back Up - coming from the technology industry we always preached to have a current backup. Be sure your phone is backing up to the cloud. I think it is free on every phone made. Consider moving all your valuable information onto the cloud. It is always with you as you travel.
I know there are many other options, I am giving you this list to get you thinking "what I need while on the road".