You are using Googles 2-step verification and this requires a phone that supports it.
What if I do not have nor like those huge shiny slabs of glass and plastic, every fashion victim drags around so happily - drooling, while finger fucking his/her phone every waking moment.
mtGox sent me a yubikey for free
I know, you probably can not do this right now but there has to be a way to fix those security issues by not forcing your clients to depend on some third party crap from Google. Especially from Google.
Even PIN provides some level of protection, when every failed attempt causes n+1 seconds delay. Add a letter to 4 digit PIN and it got way better.
I also have a free yubikey from Mt.Gox but not many sites support it.
So I'm forced to use Google 2FA and I have it installed on 3 devices for backup purposes.