Going with microwaves means no obvious PIR windows. Finally, we have [Ansaf Ahmad] with BeagleBone Black Home Automation. The idea for this project came from a calculus class on optimization.

You can use mmWave sensors to monitor presence rather than simply detecting motion.

The passive infrared (PIR) sensor market is experiencing significant growth as demand for efficient motion detection and ...

The porch light option of dusk-until-dawn sensors came into use and were followed later by motion detecting lights which used PIR sensors.