Calmness Meter analyzes brain signals from EEG headbands such as Muse S and Muse 2 to give you a simple real time Calmness Score. 

You can get a better feel of how effective your meditations are over time, or even adjust mid-way through your session.

The app can give you a gentle voice prompt or haptic feedback when your mind starts to drift.

It can integrate with Apple Health so your meditation scores can be viewed and analyzed using iOS native tools.