I've just managed to get the gear together to wire my accessories separately rather than tapping into the OEM loom. Basically like this
1. Find a wire which is live when the key is turned on - tap into this at wire it to connector 86 of a 30a/12v relay.
2. Run a wire from 87 to a aux fuse box - couple of options, use a Narva fuse box or go to a wrecker and get a motorbike fuse box.
3. Run a wire from 85 to ground -this could be on the neg terminal of the battery or a frame bolt.
4. Run a wire with an in-line fuse from the + terminal off the battery to 30 on the relay.
You now have a separate fuse box just for accessories - heated grips, GPS, 12v socket etc - just take the + line off the new fuse box to whatever you're wiring in. It will only be live when the ignition is on. Make sure the fuse you install is suitable for your new addition. Each accessory can now be fused separately.
A few proviso's - I'm not an auto-electrician just a hobbiest. Make sure all connections are clean, dry and preferably soldered rather than just crimped - and cover all joints with heatshrink tubing for the best results. Make sure you electrical charging system can handle any other accessories you wire in. Should you blow up, burn down or damage your bike in any way it rests on your head (sorry - just used to covering my arse from possible come backs).
I'll be posting this with photos in the next week or so.
Cheers