Secure DUO Two-Factor Authentication is achieved with a free DUO Mobile App:
CISCO DUO instructions and app. Users quickly verify their identity by approving push notifications before accessing applications. Duo Mobile works on every device—including smartwatches. Duo Mobile works with Apple iOS, Google Android, Palm, Windows Phone 7, Windows Mobile 8.1 and 10, and J2ME/Symbian. Download Duo Mobile for iPhone or Duo Mobile for Android—they both support Duo Push, passcodes, and third-party TOTP accounts.