I used a standard mains powered motion sensor that is wired to a standard mains powered 30w LED security light, the sensor is powered from a standard plug in my garage, at the plug face i added a power sense Zwave pocket socket
when motion is detected the power draw goes above 10w and anything i want turns on or off, i have outside LEDs, they switch from colour change to Police flash, i have other security lights all plugged into pocket sockets which also react simply via a custom device handler written by Cobra
However if you dont want a security light the pocket socket will not detect a power draw because nothing is being drawn so it wont help you
My setup has never gone wrong and is pretty cheap because all you need is cheap parts and one zwave pocket socket