Just FYI.
A speaker is the same as a microphone, it's just used in reverse, it can be reversed and used as a microphone.
Point being,... when landline phones were the thing,... all one had to do is reverse 2 wires in your connection,... maybe even in the cable trunk system far away,... and the hearing piece n your phone became a microphone, whether it was hung up or not,... that line is always live. Instead of listening to that phone you then connect those same wires at the trunk into a recorder. So,.. it's manually done, but same,... been done for decades.
Mic diaphragm and speaker cone, magnet, same thing.
In the 90s baby monitors and wireless phones could be monitored very easily with a police scanner that scan all freqs, very well and very fast, 5 seconds. AND they are so strong of output you pick up the entire house. This was corrected in the late 90s by removing those frequencies from scanners and not allowed on public devices. They may have also encrypted baby monitors.
This is nothing new, it's just a different way.