Move south. I've never run electric clothing on snowmobiles or bikes (3.5 years in North Dakota, Grand Forks AFB). Lots of people swear by it I think there was a topic about alternator load you may want to look at.
Heated Gear and GPS's usually come with the cables to run to the battery, with the gear specific plugs on the other end. Probably the best thing to do if it's for future stuff is to get a fuse block...like Blue Sea or something installed so you can just hook there instead of having to run everything to your battery and having a big mess of wires.