if you might find yourself camping in colder temperatures than your bag can cope with carry a sigg water bottle and something to insulate it with. siggs old insulation pouch could keep the bottle pumping out heat for three hours when filled with boiling water, dont know about the new neoprene pouches though. what might work better is the pot cosy stuff sold by backpacking lite, just get a piece large enough to make a pouch that can be closed at both ends, hold in place with rubber bands or plastic ties and hey presto you have a tent radiator. The caps on sigg bottles are very secure but the package could be placed in a water proof stuff sack if you are worried, you could use the pot cosy stuff as a wind shield, its light but could be held in place with a couple of pegs and your boots. A sigg bottle filled with boiled water can also be used to dry socks.
Does this win me a prize?