At this point in my training I just need basic power measurement. I don't need the refined measurements individually for left and right legs or a power value that is 100% accurate. The Garmin Rally RK100 single sensing fit the bill. The power measurement I get from actual bike riding seems to match well with the values I get from my Tacx trainer. That is to say that the same amount of perceived effort seems to register the same power values on either.
