Rohos Logon Key
turns any USB flash drive into a security key for your Mac. With Rohos Logon your Mac is protected but you don't need to enter your password manually each time you login/unlock your Mac. Rohos will automatically lock your Mac screen when USB Key is unplugged. Unlocking your Mac with a USB token is fully automatic and fast.
Note: The download link contains versions of Rohos Logon Key compatible with OS X 10.5, 10.6, 10.7, and 10.8.