It's incredibly cost-effective to just buy an old Android phone (which comes integrated with multiple microphones, with good signal processing and noise cancellation), instead of building it with components.
Haven is specifically designed for intrusion detection, and for preventing people from tampering with your laptop for instance by detecting activity on the Android phone's sensors.
Interesting concept, but the issue is that one would need to constantly charge the phone and batteries have a tendency to go bad after some time with such usage.
This was a paper from 2013 though, 7 years ago. I'm sure they've more than made it a proper technology now, with all the compute power and deep learning and what not.
Maybe unrelated, but WhatsApp does monitor your phone accelerometer data 100% of the time, even when it's in the background. An app doesn't even need to ask for permission to get access to the accelerometer data, so there's not even a pop up of any sort.
