Wearable Technology for "Real-World Research": Realistic or Not?

The article focuses on research surrounding concerns that techniques such as wearable eye trackers, mobile electroencephalography and mobile functional near-infrared spectroscopy can be used for gaining insights into human perception and cognition. It mentions that interpretation of the signal of a wearable eye tracker is difficult because it is a two-dimensional signal. It also mentions that gaze direction error, if converted to a spatial deviation, scales with the distance to the object.