I forgetted this yesterday, but better late than never.
One of my purchases for the house is quite small in comparison to the rest but will serve just as well.
I purchased this model in black. You can think of it as a door peep hole on steroids.
It contains a prism on one side (as seen on the brass model) and has a 2 3/8in viewing window on the other.
I first saw these at my place of employ. We have them in our steel security doors, mostly to make sure that no one is approaching the door when it is opened, causing an injury. You can’t quite read license plates through them, but damn near.
You can stand up to six feet away from the door and see who is on the other side of your door and what they are doing quite clearly. But the best part is that light does not transfer through to their side of the door, so they don’t know you are watching.
For $42 ($35 plus shipping), this little beastie is the next best thing to a CCTV system for your porch. Anyone with a drill, a 2 3/8in hole saw and common sense can install them in less than 20 minutes.