If I do not want to stop using flat pedals, what is a cheap (relatively) but effective setup to be able to measure power on a QX100? I would like to be able to train with power to be able to more effectively get in shape, but since my wife sometimes rides the bike and is not too sure about having to clip in, I was not sure how much I would have to change to be able to measure power at the crank or crank arm.