What for is the white brush I received with the niostem headset?

This is one of the perks that Indiegogo backers unlocked after reaching a funding milestone.

We call the white brush the "Scalp Massage Activation Brush". It can be used any time of the day to give a gentle massage to the scalp, which will help increase blood flow to it. Increase blood flow has been shown to have positive effects on combating hair loss.

The use of the brush is optional. That means it is your choice if you like the massage or not. The niostem headset can be used as recommended even without the use of the brush without compromising the results.