[rocky]

Authy is a reliable service, easy to plug-in and set up.

exsecror, you speak of it as though there are only commercial plans. One can sign up for the starter (absolutely free) plan and use it, the number of tokens is more than sufficient to protect admin area.

In any case, why not add Google Authenticator as a second option so that customers could choose which service to use. Thank you for the suggestion.