I agree, to an extent. These devices are hardly going to read minds in the sense of providing all of that detail.
However, whatever they lose in quality (of resolution), they may make up for in quantity. A poor quality device may still be able to provide some useful data points when applied to a larger group of people. Put some branding or situations inside a game, monitor for coarse grained interest or emotion, and you might have something useful to marketers or game designers. Or not.
When things like this start approaching mass markets, people start thinking of other uses for the data. Working in a field where people are spending good money trying to vacuum up all the data on the Internet, even shitty Facebook posts, I see first hand how people get excited over any new data point. Most of it is crap, but there's some gold in there, for sure.
Click-bait, but still interesting to consider.