EMG capability is now available for project bioloop - together with an extended GUI (additional diagram):

The first diagram shows heart rate and heart rate variability (HRV), while the second one shows GSR and EMG. Unfortunately the used EMG sensor from Seeedstudio (Grove) is badly documented, so the results are not as significant as they should be (orange line). Furthermore, there seems to be an electrical interaction together with the GSR sensor (green line) when both sensors are attached to the same arm, for example.

If anyone else uses Grove EMG, too, and achieves better results, please let me know...