Mob 0.7.14 has been released.

Added

• Magnetometer / compass support in Mob.Motion. Request :magnetometer
  in the sensor list and the {:motion, _} message additionally carries mag
  (calibrated field, µT) and heading (degrees from magnetic north). The keys
  are present exactly when you requested :magnetometer, on both platforms,
  and each is nil when there’s no reading (device has no magnetometer, or the
  heading hasn’t fused yet) — so a compass app matches on nil rather than
  hitting a missing key, and accel/gyro-only consumers get the byte-identical
  3-key map with no extra sensor cost. iOS uses the XMagneticNorthZVertical
  reference frame (CMMotionManager); Android fuses TYPE_MAGNETIC_FIELD +
  TYPE_ROTATION_VECTOR (SensorManager), registered only on request.
  Magnetic north only (true north needs location + declination — layer
  Mob.Location). Device-verified on moto g + iPhone SE. (MOB-6, #59)