thinking about this made me think of an iris scan instead... Mostly because I often grow and shave my beard!  A pic of your face or iris could appear on the screen and you could move around on camera, with a %50 alpha to line it up more or less... I think it could make it a little easier on the software to make a recognition.
_________________________
>Mac mini PPC / 1.42 Ghz / 1GB RAM / 74.41GB 4200rpm 2.5" / Airport + Bluetooth / 10.4.7 / 20.1" LG widescreen
>G4 400 PPC / 20 gig / 768MB RAM / ZIP drive / 10.4.7 /17" apple SD / Back up system
>Powerbook Titanium 1Ghz / 40GB / 512MB RAM / mashed up and waiting for a good mod!
>Macintosh SE/30