-Battery operated Door Bell
-5 volt relay
-Few bits of thin gauge wire.
-Soldering iron and solder
First thing you need to know is the type of doorbell you will be getting. The one i used is made by "Chime Design," model number WD-1120.
(Remote left : Receiver right)
The reason I chose this one is, the chime/receiver runs off of 3 "C" batteries which is 4.5volts. This is important that you get one that runs on a similar voltage because you will be wiring it to a 5 volt line. You can use a door bell that runs on lower or higher voltages but then you will have to get a resistor or capacitor. You may also want to find one with a single chime so your pc doesn't turn on and off repeatedly. Mine uses a "2-tone" chime and seems to work fine.
The remote is small and runs off of a single lithium watch style battery. I didn't modify this in anyway considering the battery should last quite a long time. If you want to run this in a wireless keyboard or something like that, all you need is a constant 3Volt source.
I also picked up a 5V relay from radio shack; if you don't know what a relay is, they are like an electrical momentary switch. When they are receiving power the circuit is closed and when receiving no power the circuit is open.
I made this small diagram to show how to wire the receiver and relay. Just make sure you run the positive line off of the receiver to the "purple wire" or "5V VSB" on the 20/24 pin connector on your power supply. This wire sends a constant 5 volts to your motherboard when the power supply is plugged in. You can use any ground wire (black) on your Power Supply.
Thats it. Its a really simple cool addition to any computer.