i believe in another thread someone said the the whole light turning off thing is that the light from the bulb reflects off you and back to the sensor tricking it into thinking its daytime, and thus turns off.. but once you walk away.. light is no longer able to be reflected into the sensor as well.. it was on before you were under.. so when you left the old condition has returned.
The watch thing.. I dunno.. thats weird. I also can't help ya cause I dont' wear watches