I'm using the Seadog motion sensor to control floodlights. It will false alarm occasionally. I have it set up on a ball-joint mount to get it aimed correctly to cover my deck. See the attached schematic.
Hmmm. I hear movement. Birds wake me right up. Any odd sounds in the water wakes me right up. Any boats nearby or a tap of something touching the hull wakes me right up.
I guess these devices help you get better sleep than I do, so they make sense