(*) Easy to use. A one-command setup, one environment variable,
  and it just runs in the background.
(*) Indestructible. Tolerates unplugging, sleep, and suspend.
  Never needs restarting.
(*) Compatible. Provides a public key that works with all services
  and servers.
(*) Secure. The key is generated on the YubiKey and can't be
  extracted. Every session requires the PIN, every login requires a
  touch. Setup takes care of PUK and management key.

WWW: https://filippo.io/yubikey-agent