The FAQs state that you need Android 4.4 or higher and 5.1 or higher is recommended.
I haven’t personally used these particular e-tickets but some of the other FAQ items should give caution to
anybody planning to use them
a) You need to activate the ticket, just before you ride. Once activated the ticket has to be used in a very specific time interval without any refunds. Unless the activation is an offline time-based thing…you will want to make sure that you have
good cellular signal or WiFi access at the station.
b) You are responsible for making sure that your phone is properly charged and does not enter any power saving states as the activated ticket must display in its multi-color mode when presenting to the conductor.
c) You are not allowed to keep your device in airplane mode.