This Keychain Puts Eyes on the Back of Your Head

Did you know that predators have eyes on the front of their heads and herd animals, being prey, have eyes on the sides of their heads? That cow munching on grass has more than 300 degrees of view, so it can see predators approaching from anywhere but directly behind. But you, as a measly human, barely have more than 200 degrees and that leaves you vulnerable. To reduce the risk from predators of all sorts, Ayushmaan Bhardwaj developed the RearSight keychain.

RearSight is a device that effectively gives you eyes on the back of your head, so you can see what is behind you. It is great for walking down dark city streets at night, or bear-infested forests at any time. Simply hang it from your backpack and start your journey. It can notify you if it detects a (human) face and you can use your phone to check the live video feed at any time.

I like to keep things light, but that has genuine potential for improving one’s safety.

It all works thanks to a DFRobot ESP32-CAM development board, which has a built-in camera to capture images. Power comes from a lithium battery and there is a TP4056 module for charging. The last component is a DC-DC boost converter. Those components all fit into the stylish 3D-printed shell.

The big caveat here is that all of the functionality requires network access to a computer running a Python server. That performs the face detection, sends the push notifications, and hosts the dashboard where you can view the feed. The ESP32 connects to that via Wi-Fi — either locally or through the internet — and you can potentially use a hotspot on your phone. But the use of a separate server does limit the “out and about” practicality of RearSight.

It would be nice to see a version that works entirely locally. Face detection would be tricky for the ESP32 to do on its own, but publishing a live video feed to a self-hosted web interface is definitely doable.

Even as it is, however, RearSight could be useful to many people until we humans manage to evolve eyes on the sides of our heads like our bovine brethren.