Features Supports one-time passwords from a variety of sources Yubikey support Google Authenticator support SMS support (using Twilio) Phone support (using Twilio) Phone/SMS can be used as a backup source as well Paper one-time passwords can be used as a backup Full example application provided (try the demo) Very flexible, use only the features you need Easy configuration in application.rb Sample app works out of the box (including on Heroku)