Entropy of Androids motion-sensor data
Read Toward Sensor-Based Random Number Generation for Mobile and IoT Devices, if it's not too late(!)

In summary, the extracted table below shows their findings.  Those were that the three accelerometers in combination provided a good 24 bits of entropy for randomness extraction.  The good bits are the black boxes in the table as per the note below it.  The team got fairly good random results from their scheme.



I'd add the proviso that they used aggregated data from 37 devices.  The results for a single device might vary...