Sorry for not updating for a while since I got really busy and [standard excuses]. Anyway- I have moved so I need to revise my overall design and instead of actuating the door knob it would make more sense to have it actuate the deadbolt in this particular setup for my new apartment.

I've done some more testing and found that intense network traffic can overwhelm the cheap-o wifi dongle and it will start dropping packets (for example, a roommate watching netflix on the couch will just overwhelm it and it will completely miss most/any authentication packets). 

So here is what I am thinking now- create a aluminum foil overlay that goes over the back so the exposed part of the  antenna facing the door. If I'm correct this should help block out traffic from inside the apartment (since there tends to be a lot of it). That way, in theory, the only the traffic that gets sniffed is directly from the phones outside the door rather than inside the door.

I also picked up a small motion detector from amazon for a few bucks. It's fully digital so just provide it voltage and ground and it's a simple high and low on the output pin- which means it can be attached to an interrupt! I'm going to assume that you know what interrupts are but if you don't know- here's a good resource to learn more.

I did some short experimentation with the sensor and an Arduino and found it worked quite well. The idea is to use the motion sensor to turn on and off the polling of the knock sensor and maybe sleep and wake the raspberry pi for power/heat reason (I've noticed the pi tends to get a tad warm). But I'll see if it's really neccesarry in the end.

Now that things have calmed down and I'm not on vacation or moving I can start working on it again.