"pam_fprint is a simple PAM module which uses libfprint's fingerprint processing and verification functionality for authentication. In other words, instead of seeing a password prompt, you're asked to scan your fingerprint."
The idea is to use the built-in fingerprint reader in some notebooks for login using PAM. I will also explain how to use regular password for backup login method (solely fingerprint scanner is not recommended due to numerous reasons).
First, make sure you have one of the supported finger scanners. http://www.thinkwiki.org/wiki/Integrated_Fingerprint_Reader gives a list of supported devices. To check which one you have, type
You need to install pam and libfprint. In my case PAM was already installed.
# pacman -S pam libfprint
Once you made sure your reader is supported, you are good to go
# pacman -S pam_fprint