As i put a lot of thoughts in this project, and since there was not much choice cc the different components, i'll try to clarify here what i did exactly to make this work:
What you'll need (with links + pictures)
- This peephole Sony Cam:
https://www.amazon.com/Shrxy-800TVL-Cam ... ephole+cam

- This USB Video Grabber:
https://www.amazon.com/LOGILINK-Grabber ... with+Audio

- Don't forget this BNC-M to RCA-M adaptor (of course you could pick anyone you'd like depending on pricing:
https://www.amazon.com/Coupler-Adapter- ... o+rca+male

I actually picked the wrong one with female RCA so i simply put a 'yellow' RCA cable (M-M of course) in between the Cam and the Grabber
- Optionally you can pick up a touchscreen of your liking, i chose the official 3.5" touchscreen with the chassis that fits the pi and the screen perfectly and connects exclusively over GPIO - for example if you want to have a monitor mounted directly on your doorside to actually see what's going down on the other side:
https://www.amazon.com/Kuman-Resolution ... B+%2B+SC11

- And of course the Raspberry Pi - i opted for the Pi 3 Model B for the build-in wifi (since you have to mount the Pi on the door and you do not want to add extra cabling) - i think i don't need to add link or picture
- Optionally add the a power supply with on-off switch just for practical reasons and yeah, you need another universal 12V power supply with some adapter choice to actually power the camera (12v for a cam is a lot that's true, but hey, who cares..) - this is the suboptimal part, where you actually need two power sockets near your door, which i didn't have so i simply put cable trays and it doesn't look too bad) - don't forget to switch the universal power supply to 12v since mostly that has to be done manually on that kind of power supplies (jfyi)..
Now comes the interesting part, and believe me, it was way easier than i thought.. If you picked the hardware i described, have set up your Pi under Raspbian (Debian should work too cc the Video Grabber's drivers, but didn't tested that), have ssh access (preferably without password and public key authentication only), set up the touchscreen drivers (if you're planning to use that), you're good to go..
Next step is to set up 'motion' software (that's the name of the software, you can check for it: apt-get update && apt-get cache search motion, it should be there somewhere on the repo list if it's up to date) and follow this guide to set up motion software and live stream (grabber video is under /dev/video0):
http://www.codeproject.com/Articles/665 ... nce-camera
I actually only use the live stream feature at the moment, and it works quite well @10fps (i think i can go to 15)
To mount this setup on your door, you'll have to either drill a new hole, or extend your existing hole, since this cam is a bit larger than normal peepholes - and longer by the way, so a part of the camera is coming out on the inner side of your door.. I choose to build a little plastic chassis for all the components (except the pi and its touchscreen) and i simply used double sided tape to fix all this (all is super light so it will stick)..
What you can do to your liking is the motion software config and recording the video (preferably to an NAS or another PC) eventually only when motion is detected, otherwise you're going to have huge amounts of data written constantly.. There are little scripts out there to do just that on a scheduled basis (just use crontab) or with motion software itself, but i'm not there yet, eventually i'm going to update this here..
So those are my two cents, if anybody is going to try the same, i can confirm it works out of the box and can be done in like an hour or so..
Sincerely,