If you get a fingerprint reader, you can set up a fingerprint authentication functionality to Ubuntu, including a seamless integration into GNOME 2.x, Unity and GNOME 3.x using FPrint.

you need to have a supported fingerprint reader. Supported devices are:
045e:00bb 05ba:0007 08ff:2580
045e:00bc 05ba:0008 08ff:5501
045e:00bd 05ba:000a 1162:0300
045e:00ca 061a:0110 138a:0001
0483:2015 08ff:1600 147e:1000
0483:2016 08ff:2500 147e:2016

First press Ctrl+Alt+T to launch a terminal, add this ppa (for now, supports lucid, natty, oneiric, and precise) to your sources:

sudo add-apt-repository ppa:fingerprint/fprint
sudo apt-get update

Then install the software:

sudo apt-get install libfprint0 fprint-demo libpam-fprintd gksu-polkit

Launch fprint project demo and check that you can enroll and verify your fingerprints and that your reader is indeed supported.

In top right corner, go to System Settings -> User Account setup “Fingerprint Login”.

That’s it! Test it: Lock and unlock screen, log out and back in, try sudo in terminal.

Read the description on this FPrint PPA for more informations.