Login or unlock screen on a Mac using an NFC tag? Does OSX have support for unlocking the screen (or logging in) using a NFC or RFID tag?

The ACS ACR122T USB NFC dongle (a PC/SC device) seems to have working OSX drivers, but no software suite for login is available.  Rumors has it that Dangerous Things are working on that.

A workaround is to use a RFID/NFC reader that acts as an HID/input device, such as the RfidLoginer.  But that doesn't sound very safe, especially since the linked device only sends the RFID device ID.
In earlier versions of OS X (i.e. 10.9 and older) you had the /usr/sbin/pcscd executable, which the driver that comes with your ACR122T dongle can talk to.

In the latest OS X (10.10), pcscd has been replaced by something new called com.apple.ctkpcscd, which will be running in a default install of Yosemite.

The documentation for this new daemon is available from:

https://smartcardservices.macosforge.org

Here you can also get the source code, etc.