I've just spent a while putting heated grips on my Interceptor, and took the switched power feed to the relay from the pilot light in the headlamp. It was only when I finished that I noticed a spare connector in there. Looking at the wiring diagram, I see it's a switched accessory socket, rated at 10A.
So, if you're thinking of adding electrics, just be aware that there is already this connector for you to use. Yes, it's only 10A, but that's probably enough for sat nav, heated grips etc...
The lesson for me is RTFM !!