by the way, Intel's Quark chip is installed at least 3 times on each chipset and can run on a Minix OS when plugged in to the power and off:

from: https://web.archive.org/web/20201201175708/http://blog.ptsec...

Highly efficient" is 25mW at 33MHz. According to the Wikipedia page, it can run even when the PC is off but plugged in or connected to battery. an ARM Cortex M0-4 will use even less power in idle. All it needs is a tiny capacitor and bootrom and a secret flash storage to record audio and upload it once internet becomes available

"The Intel Management Engine always runs as long as the motherboard is receiving power, even when the computer is turned off. This issue can be mitigated with the deployment of a hardware device which is able to disconnect all connections to mains power as well as all internal forms of energy storage. The Electronic Frontier Foundation and some security researchers have voiced concern that the Management Engine is a backdoor.

Intel's main competitor, AMD, has incorporated the equivalent AMD Secure Technology (formally called Platform Security Processor) in virtually all of its post-2013 CPUs."

https://en.wikipedia.org/wiki/Intel_Management_Engine

There are countless low or passive power audio devices since the Thing that can record and upload/bounce audio to receiveing devices: https://en.wikipedia.org/wiki/The_Thing_(listening_device)