Printing out tickets as a backup. I do this for concerts and travel because then I don't have to worry about batteries dying, wifi/roaming not being available, getting logged out and having trouble getting back to the ticket, etc.
I also print out maps when doing wilderness backpacks because even if you download the map you'll burn through your battery life well before the hike is over but a paper map is just as good. If I really need to confirm my location I can occasionally turn on the app and shut it off. I keep the maps in a gallon ziplock so water isn't an issue.