Peephole Motion Detector is a free camera application with a built-in motion sensor that allows you to turn your old smartphone into a fully-featured surveillance camera in just a few minutes. It detects motion in the surroundings and takes a burst of still captures, which are then sent to a pre-configured email address. The app also keeps the pictures in full resolution on the device for later analysis.

This app is ideal for use as a peephole or door camera, as it requires no extra hardware or modification to your door. Simply mount your old phone on top of the existing peephole, connect the charger, and you will always be the first to know if there is any suspicious activity at your door, no matter where you are as long as you are able to receive emails. It can also be used as a baby monitor or for any other security camera application where you want to be informed if there is motion where it should not be.

However, it's important to note that this app is not a webcam, does not record video, and won't make you a coffee. The free version is fully functional, but configuration options are limited. The premium version offers loads of customization options, including configurable motion detector parameters and a detection area editor.