1) No matter how long your extension cord is, it's always three feet too short. My project adds six feet to any extension cord. If you build one you can make the cord as long as you want. Just remember to derate the power of the appliance accordingly.
2) No matter where your extension cord is, you can never find it. Now I have an extra one in case I can't find my other one or if the other one is in use.
3)Some appliances do not have an on/off switch. I am doing some experimenting with hydronic solar thermal collectors and the pump I'm using does not have an on/off switch. To control the pump I have to plug or unplug it, which is annoying. Other things that usually don't come with switches are soldering irons and hot glue guns.
This project is safe because all materials used are CSA approved, the device is properly grounded, wires are properly sized and an appropriate strain relief device is used on the cord.
This project is quick; it only takes about 15 minutes to complete.
This project is simple with only a few components and straight-forward wiring.