Consumer vs Medical grade
>>Fitbit's CEO James Park has said that: "People need to use common sense. It’s not a medical-grade device; it’s a consumer device. In that setting, it works incredibly well."
There's a serious problem with that statement. Usually the difference between a consumer and an industrial product is that the consumer product is made of far cheaper materials and will break much sooner. As opposed to being completely unfit for purpose.
If the device is supposed to tell me how fast my heart is beating then it should be able to do so within a reasonable deviation. If it can't do that then it shouldn't be used at all.