The module's pinout seems to be:
- 3V3 - module power supply
- GND - common ground
- OUT - outgoing light voltage
- IN - incoming light voltage
- CDS - light detect / module disable feature
As far as I can currently tell, it works something like this: if the CDS is not pulled low, the module will send out pulses and measure their return times. If a change in return times is detected (i.e. something in the path of the radio waves has changed position), it will connect the IN and OUT lines (most likely with a MOSFET). So if there's a light connected to the OUT line, and an external power source (4V - 28V) is connected to IN, it will light up. The OUT line will go low after a short period of time (a few seconds) if movement stops. Of course, GND lines must be connected together.
I'll need to experiment with it some more.