Comment 3 for bug 187130

After realizing that this needs to be done with your thumb rather than any other finger, I got this to work for myself on an M09 system using the packages in the PPA. Works fairly well.

A few things stick out about this implementation:
 1) The login screen's new phrase "password or swipe finger" is too wide for the default theme
 2) gksudo doesn't indicate that you can swipe instead of type a password (although you can)
 3) The old "[sudo] password for $user:" prompt is missing the [sudo] prefix.