Originally Posted by
NWIFlyer
Nor me, and with the advent of high capacity power blocks, and many more trains having charging points, it's increasingly unlikely that your phone would completely run out of charge with no method of restoring a few percent fairly quickly.
The app (at least the Android version) does not allow you to screenshot the photo page, but you can grab an image of the previous screen which shows names and card expiry as a back up if the app does malfunction.
I think there are people whose phones often run out of battery, and those who don't. You already know which category you fall into, and can judge whether or not you want to use this app accordingly.
I do need to get a new phone, though. 4 years old, and the battery is starting to struggle!