Can't work for me.
I have a celI rarely use text, so paying $15 for a chunk of texts I'll never use is stupid.
I'd allow pay-per-text, but only if I only had to pay to SEND - I refuse to pay per-message for someone ELSE (perhaps spammers) sending to me.
As a result, I have texts/SMS through my cell carrier BLOCKED.
Instead, I use google voice for the one or two people I *occasionally* have to send or receive a text from.
Heck, I don't even use my direct cell number for calls - I consider the number disposable, and use the google voice number instead. If I have to switch cell carriers, no mess giving people a new number - only one or two direct family members, for use in the very rare instance where there was an emergency AND google voice was down.
So this is completely useless to me - trying to use the GV number for the 2-factor would be problematic since I have to have access to my google account to be able to see those text anyway.
Something which helps protect against someone else accessing my account is great, but it absolutely has to first have an absolutely failsafe way of ensuring that *I* never lose access to it. Printed-out codes can be lost, as can cellphones and dongles.
Right now my solution is to have a very good password which I absolutely remember. I suppose if I were to ever lose my memory that could be an issue too.
I don't know what the solution is. Clearly neither does google or anyone else.