"Wait!" I can hear you exclaim. "Heated grips? But you've got heated gloves, for goodness sake! How much heat does one person need?"
Well, these were on the bike when I purchased it. If you don't ride in winter, you probably won't need them. I found that the palms of my hands became unpleasantly hot whilst the outside froze; that's why I went for the heated gloves. In REALLY cold weather I use both.
The controller died recently, and to replace it with an OEM type was too expensive in my opinion. Instead I bought an Oxford HotGrips kit. All I needed was the controller, so I sold the HotGrips themselves on Ebay. Surprisingly there was a bidding war, and the final price covered the entire cost of the kit - so in effect I got the new controller for nothing.
Which was nice.
The wiring needed some slight modification as the connectors were slightly different. The original wiring also ran straight from the battery, so I re-routed this to the auxiliary fuse box. It also means that the battery will not run flat if the heated grips are accidentally left on when the ignition key is removed.