Using strong passwords and an auto-completing app like keepass, this is simply not an issue. I can log in from another device.
Also, reliance on mobile devices means reliance on some corporation's cellular network. Putting the control of your vital access into the hands of people who you know are not your friends and who would love to take more than just your money is never a good idea, in my opinion. When their system crashes you can't just reboot your phone to fix the problem, you can't do anything.. in fact. You have to sit and stew in the hell of your creation until their system magically comes back online. Not worth it.