Security technology has been really moving forward lately for both home and commercial use. A prime example of this is the Face Recognition Door lock. While this is designed more for the commercial market, it could be adapted to home use fairly easily.
The enticingly named Model CVJB-G107 is designed for use as an employee timeclock, and bases its facial recognition off of a 2D photograph. Equipped with night vision, TCP/IP compatibility, and the ability to register up to 500 faces. Hopefully your family isn’t that large, but it could be useful to keep out you cousin with the plate in his head that keeps showing up every year.
Currently available for order online, expect to pay around $500 unless you buy in bulk.