[titaniczero]

Try any voice recording app for a few hours, now use the facebook app for the same number of hours. The impact on battery life of a mic actively recording alone is very noticeable, so noticeable that your phone has a special chip just to recognize patterns similar to “hey siri”.

[Melatonic]

It would not need to record high quality audio and could maybe even take advantage of that same chip? Just thinking out loud here - smaller, crappier audio would also be easier to send back unnoticed (or instead of even recording audio it could be transcribing on the fly to a text file using something super basic and easy with low accuracy)