Unlock door by data from peephole + knocking, possible?

Hello arduino folks!

I am just about getting started with arduino and I am really excited about it, I'm new to setting up your own hardware technology and everything but I have knowledge 'bout programming. I will of course start out by creating simple set ups with LED-pins and everything but before I start I am just curious to know if it would be possible to set up an extern lock mechanism to a door which would unlock the door when I hold the hand before the peephole or point a flashlight against it and at the same time may be knock two times at the door?

As I said, I understand that this is an advanced project which it will take time for me to get to but hey you gotta ask if you want to learn :)

Thanks! /A

There was a project a while back where someone used an Arduino to make a door opening mechanism that would unlock on the right knock combination. Probably something to look at for inspiration and ideas.