i was curious about the pod on the chainstay, but I guess that's the polar power thingie. I read that it measures power by checking the vibration of the chain. Makes sense, since you enter in the length/weight of the chain it's a simple physics calculation. But does this assume a clean chain? what happens when the vibration is damped by mud or grit? or the weight of the chain+mud changes?

--edit- yes, I'm a nerd. I found one of their patents, 6,199,021. they're using Force = 4 * mass of suspended chain * length * frequency^2, where the measured aspect is frequency, and mass/length are assumed to be constant.