I can't really help you with choosing a HRM, as I personally, hardly ever use one (my bike computer has it, but I don't use it very often). But I was just curious as to how the cadence option would work for spinning? I take spin classes 3x/week, and I just don't see how cadence would work in that situation...unless you were to somehow attach a cadence sensor to the flywheel???Is that what you are looking to do?