As has been mentioned before, there is support for some fingerprint readers via 3rd party
devel/libusb based projects.. libfprint.
If you check the ports tree, there is an example fingerprint authentication port.. allowing you to login using a fingerprint (..biometrics is just a fad, it's not truly secure).
For the adventurous, see
security/libfprint and
sysutils/login_fingerprint.
You should also check their homepage, they have some utilties that haven't been ported.. but should still compile.
http://reactivated.net/fprint/wiki/Main_Page
Note;
ugen(4) is a driver that all devices attach to if no other driver can.. it's a generic fallthrough device, libusb based programs can only access ugen(4) devices.
Hope that helps.