Simple daemon for locking and unlocking OS X with Yubikey.
Via Homebrew formula:
When you attach Yubikey for the first time launchctl will run yubikeylockd daemon that will simply monitor the state of the Yubikey USB devices. Daemon based on the sample provided by Apple for IOKit development.
It does two things:
IOPMAssertionDeclareUserActivitycall to turn screen on
IORequestIdleto put display to sleep and (if you configured it) also locks the OS X