Espressif’s ESP32 microcontrollers come with a Flash encryption feature that when enabled ensures that the data and code stored on the (usually external) Flash chip is encrypted with AES-256 … ...

How it works is simple: you can track devices using Bluetooth on the ESP32, and through a combination of presence and signal strength, you can define a sensor that changes to an "on" state when ...

I've been playing around with a couple of ESP32 microcontrollers, and that experimentation has taught me a lot about sensors and what you can build for really, really cheap.