Just like in a car, the cigarette lighter can be used to power a whole bunch of accessories such as heated vests, radios, etc. If you don't have the item hardwired to the bike, then you need to have a socket or two available.

There are two basic sockets on the market right now. There's the standard cigarette lighter socket and the smaller BMW style powerlet socket. Each of them provide 12v of potential, but they each also take different plugs. Many motorcycle accessories today use the powerlets, because they snap and hold into place - very handy on a speeding, vibrating motorcycle. I choose to have both, just in case I need to charge my cellphone or whatever.

The below picture shows the powerlet installed just below the right glovebox. Like most powerlets, it has a spring-loaded flip-up lid to prevent water from getting in.

The next installation is of a dual powerlet panel that installs on the left side, just below the seat. The knob you see is the rear shock adjustment knob. This particular installation is great for rider/passenger vests because A) there are two of them and B) it's mounted on the left side, which is where most vests have their cords.

The final place I installed a power socket is at the bottom inside the right glove box. This is a standard cigarette lighter socket with a waterproof cap. This is great for charging things like a cell phone or powering a radar detector.