4 types of sensors for short or long recordings:
All of these sensors can be used for short recording (less than 30 minutes):
mainly designed for coherence and breath training.
Long recording (up to 8 hours and a half), can only be done with the use of a Polar chest strap or a compatible Bluetooth chest strap device.
The pressure wave (related to the Mayer wave or Cranio-Sacral wave) can only be displayed with the Berry BM1000C finger sensor (best accuracy - available January 2017),
the iHealth finger sensor (less accuracy - much sensitive to movements)
or the Camera sensor (less accuracy - much sensitive to movements).
Short Recording options of the app has been designed for quite & calm recordings (as slow breath trainings, heart coherence, relaxing or meditating states). If you want to make a recording while moving, it is better to use a bluetooth Polar Chest Strap.
The light sensors devices (iHealth finger sensor, the earclip sensor and the ios camera)
are very sensitive to movements of the sensor:
they need a special care when used to achieve a good acquisition of data.
Mayer Wave acquisition can only be achieved in a quite & calm relaxing or meditating state.