Thank you Steve.
I haven't received my new F800GS yet (it's arriving at my dealer any day now) so I don't know where I'll be installing my fuse block and other stuff. On other bikes I've sometimes taken the trigger wire off the rear running light and that too has enough power to work well and it's instant on/off with the ignition.
Anyway, bottom line is that I'm not going to use the GPS connection as a trigger or the accessory outlet. So it'll either be the headlight low beam as you suggest (most probably) or something else.
My dealer tells me that there's no service manual from BMW yet which includes the 2013 model F800GS but he's going to order one for me when it does become available.
Originally Posted by Schai
In my opinion, the best wire to control power that wants to go off immediately with the engine is the power to the headlight low beam. It comes on as soon as the bike starts and goes off immediately when you shut off. It has enough power available to supply any control circuit or relay. "As I remember" (famous last words) it is available in a few places, like on the harness going forward to the headlight. It also might be available under the seat on the left side. My Clymer manual has the correct wire color (I guess yellow) but we just got a bunch of snow and the book is out in the garage and it's after 3am. I've got it all taped up now, and didn't discover the Clymer manual with a Real Wiring Diagram until after I'd had to poke around a lot.
The wire to the accessory socket is handy, just not the proper wire.
I hope that this helps. Good luck.