Microwave Radar Module from ICStation.com
JLCPCB Prototype for $2(Any Color): https://jlcpcb.com
Interesting microwave sensor module which uses a LM2596 to switch the output.
http://www.icstation.com/microwave-radar-sensor-module-human-body-induction-switch-delay-time-sensing-distance-voltage-adjustable-switch-controller-p-13727.html
http://www.ti.com/lit/ds/symlink/lm2596.pdf