As for heart rate you would think it is easier but again I guess it would depend on the fit around the wrist and the position on the wrist to determine it accurately.
I don't really understand why people are suing over this. If your heart rate is 160 and your Fitbit is saying it is 80 then you return it for a refund or replacement. You don't train yourself to death.
It is a bit like if your sat nav says drive a across a field then into a river.. you should be using your judgement - not deferring it to some device.
If you are struggling to catch your breath or feeling a bit funny then typically you would ease up rather than run yourself to death on a devices say so. I would hope that most people are smart enough to determine that if they can feel their pulse pounding and the monitor says you are barely above resting heart rate then something is probably incorrect with your device.