Sleeker designs in some of the new QS devices is see being promoted, especially those on sites like Kickstarter, lead one to be highly skeptical of their accuracy.
Some people think accuracy is not that big a deal, but it will become more important as QS devices look deeper into what is going on inside our bodies. You need good algos for that.
The link in Robert’s comment is to his excellent blog post on his site “biotinker,” and I’m relinking with different link text to be a bit more transparent and also more easily searchable: QUANTIFIED SELF ALGORITHMS ARE NOT EASY: A THOUGHT EXPERIMENT.
Reporting some kind of score rather than a verifiable measurement (like a step count, or even the number of calories burned) does seem like a cop out, but “as long as the number is higher for more activity and lower for less activity, I’m happy”. I think that’s actually quite a high bar to set
Kickstarter projects don’t get funding by setting realistic expectations; I hope that won’t lead to a backlash.