Install a 3way switch. Feed the point; one traveler goes to the unit feed and the other traveler goes directly to the backside (output) of the detector. This gives you two choices: motion and always on. If you want a shut off switch make it a 2 gang box and put a plain single pole ahead of the 3 way. Make the output of the single pole feed the 3 way's point.
#25312 - 05/04/0309:45 PMRe: Manual Switch for Motion Sensor on Light?
I've tried that setup, and on some brands of motion lights (Heath/Zenith in particular), applying power to the load side of the control module results in immediate damage to the controller electronics. The light will then no longer work in motion mode.
The 3-way setup works with most brands of motion lights, but not all!
#25313 - 07/14/0310:44 AMRe: Manual Switch for Motion Sensor on Light?