This is an interesting research paper about the feasibility of recording sounds with Android gyroscope without the authorization of the phone owner. I haven't read the whole paper, I skimmed through the experiment setup, nothing seems complicated. Enjoy reading it.
The abstract:
We show that the MEMS gyroscopes found on modern smart phones are sufficiently sensitive to measure acoustic signals in the vicinity of the phone. The resulting signals contain only very low-frequency information (<200Hz). Nevertheless we show, using signal processing and machine learning, that this information is sufficient to identify speaker information and even parse speech. Since iOS and Android require no special permissions to access the gyro, our results show that apps and active web content that cannot access the microphone can nevertheless eavesdrop on speech in the vicinity of the phone.
https://crypto.stanford.edu/gyrophone/files/gyromic.pdf
