For anyone who has done any extensive photography in very cold weather (weather below freezing), I'm sure they have encountered "sluggish battery syndrome". This is where the camera battery, when it gets cold enough, runs down quickly and delivers poor or "slow" power to the camera.
I was out in my yard photographing the resident birds when I encountered sluggish battery syndrome on my 7D for the first time. This is a weather sealed camera, so it holds up pretty well. The temperature today is about 24°F (-4°C), and while I was able to photograph the birds for about an hour, after that my camera rapidly went from functioning perfectly well to behaving extremely sluggishly. A couple times the mirror seemed to glitch out mid-exposure, resulting in half-exposed frames, or the camera would simply stop functioning, requiring me to turn it off and back on. When that happened, I came in and warmed everything up, and it all seems to work perfectly fine now.
I'm wondering if there are any tips, tricks, or handy contraptions that can combat this when photographing outdoors. Beyond the run of the mill "Keep an extra warm in your pocket and swap back and forth", which only works for a while before you just don't have enough juice to do any real photography.