I've been trying to use two factor auth for my apple devices and account.
But, it doesn't work as apple say... eg, apple says once you have authenticated a device it never asks you again.
This is wrong, i always get asked for the stupid pin code no matter how many times i've entered it.
And, there is no email authenticate option, so I'd be stuffed when overseas on a local sim card or when the phone is not nearby.
It has been too much trouble for me, so I'll switch it off I think. I like the idea of it, but in practice it is way too annoying and the implementation is poor.