Seems most people at cocoontech recommend a separate motion detector, from the light - not combined. Though, I've seen a few people use the combined unit. As Stamp said, it would allow you to use it as a trigger for multiple events, e.g. notification and lights. I don't know how you'd use it to trigger a camera - lights, camera, action...camera motion detection, from what I've read about newer camera systems, is that the motion trigger is incorporated into the camera software.
Nexus, are you using HAI?