That's not entirely true -- there are some applications of the Epoc that can actually perform detections which cannot solely be attributed to facial muscle movement. [1] Of course, the signal-to-noise ratio is much lower than that of research-grade devices, so a lot of preprocessing is required.

[1] NeuroPhone is an example: http://www.youtube.com/watch?v=tc82Z_yfEwc. Here's a peer-reviewed article describing the preprocessing involved: http://sensorlab.cs.dartmouth.edu/pubs/neurophone.pdf