Is there any downfalls to using a dedicated cell phone with the controller? I can pick up a Samsung Galaxy J3 for 79 bucks. I plan to trow an old deactivated SIM card in it so it won't have internet. I figured it may reduce any potential app conflicts that may happen with my work phone. What happens if you don't have service to load the pre flight location map?
You can always load the map wherever you have data coverage, then it will be waiting for you when you go to fly.
For my iPad I have a cheap SIM, which is a pay-as-you-go type one, just so I can load the maps at the point of flying, then turn it to Aeroplane Mode while I am flying. If I use less than $10 of data per month, it rolls over to the next billing cycle for up to 3 months, then they charge my account.