In defense of the fire piston (disclaimer: don't own one) - it works great for sparking tinder, its very reliable for that. Fire Piston + sticks, not so much.

Candle cracking from cold - consider packing a contained heat source, like this emergency candle http://beprepared.com/product.asp_Q_pn_E...rgency%20Candle better yet imho a sterno type can, that's what I have in my car kit.