YubiKey NEO is a dongle that supports both contact (USB) and contactless (NFC, MIFARE) communications to secure your Windows, Mac OS or Linux computers and/or Android/iOS smartphones using two factor authentication. It supports one-time password (OTP), smart card functionality (OpenGPG, PIV…), as well as FIDO Alliance’s Universal 2nd Factor (U2F) protocol.
The key can be used in a variety of applications, such as logging into your computer, accessing gmail, github, dropbox, and other accounts, and disk encryption. It also works with password manager such as Lastpass or Dashlane. You’ll need to both enter your password, and connect the Yubikey to your computer to be able to login, and for NFC enabled smartphones, you’d need to tap the key on the device.
In case you lose your key, online services usually have recovery mechanism in places, and some support registration of up multiple YubiKeys. The latter can probably be used for local disk encryption and password, just like you may have a spare key for your car or house.
Yubikeys have been around for a few years, but I’ve just discovered it via a recent Nobert Preining’s blog post explaining how he secured his Debian computer, which now requires the key to login, send PGP signed emails using GnuPG (keys are stored on the key not the computer), and uses Timed OTP to access services like WordPress, Google, or Dropbox. He also installed OpenKeyChain and K-9 Mail Android apps to send secure emails from his phone using NFC authentication.
You may want to visit Yubico website for further information.