I have one of these buttons.
I've successfully hooked up the 2 power button pins to pins 3 and 4 in the GPIO and a few lines of python later I have a button that turns the device on and off (holding it for a few seconds to turn the pi off). That works great.
The button also has an LED light. In the PC motherboard you just connect the pins to the motherboard header. My question, can I assume that this led is meant for the appropriate voltages and I can connect it directly to the GPIO pins without a resistor? I would then just program the LED to light up when the device is on.