Inside an LED lamp with PIR body detector.

There seem to be a modestly wide range of these lamps available on ebay, so it's worth taking a look inside one to see how it works.
The most notable features are the use of a standard 3W LED driver with a simple resistor and zener based dropper to give a stable 5V supply to the electronics, both in standby mode when the 3W PSU puts out an open circuit voltage of 15V and when the LED array is lit and the voltage drops to 9V. The sensing circuitry is based on the very common BIS0001 or BISS0001 PIR controller with its usual support citcuitry.

This item was another part of the goody bag sent over from China by Judd (an Australian living in China) so I'll provide a link to his Alibaba store. Although I'm not sure he has these on it.
http://anboge.en.alibaba.com/