Please make a million dollars on my idea (Score 1)

Why not have one of those fingerprint readers replace the door bell.

if fingerprint_match() then
      unlock_door()
else
      sound_bell()
fi

Abnormal scenarios:

1. What about power outage?
use your key

2. I am so drunk my fingerprints don't work, my dog ate my fingers, and other excuses?
a. The doorbell will ring
b. use your key