What are some good two factor methods for logging onto your Mac?
How about something like Knock?  http://www.knocktounlock.com
It's not exactly the same as looking up a time-dependent code, but does require the 'second factor' in order to unlock.

The neat thing is that many apps (I think Knock included) run on Bluetooth, so when you walk away from the Mac and the BT disconnects, it automatically locks up the machine.