Frontalis contraction with anxiety can be also studied with both Muscle SpikerBox & H&B SpikerBox, because Frontalis contraction will produce EMG signals and anxiety can affect EEG which can be monitored.

Corrugator muscles during worry are contracted, thus producing EMG signals, but we didn't do that type of experiment yet, so it would be one great study. Also in some way it's pretty neat that they are really close to the forehead's skin and could be easily detected.

Here is an idea for your next project - influence study of anxiety on Alpha brain waves