I have concerns about using a pixel and these concerns may be wrong.

With the pixel, the battery can't be removed from the phone. Also, even if the phone battery is off, many motherboards have batteries on them that are different from the phone battery.

Does the circuit board of the phone allow any hardware access to the cellular modem in the absence of software?

So here's an example of something that wouldn't be able to access the modem without software:

Hardware-----

Hardware----- ----> All data gets sent to chip that can't function without software ---> Cellular modem

Hardware-----

Here's an example of hardware that could access the cellular modem even if software doesn't allow it:

Hardware <-------------------------------->modem
(camera) ^
^ -

-

-

*
CPU<------------------------------------------>software

*should be down arrow thing

i don't know how to make the graph look normal. the first one should have cpu in between hardware and modem

the second should be a box and hardware can access modem from hardware like camera to modem or from software to cpu

In example one, hardware has no direct electronic connection to the modem and in example two, it does have direct access both by connecting to the CPU and then software but also by connecting directly.

This is probably a bad example and I'm not a circuit designer, so please don't accuse me of spreading misinformation, because I am not claiming this and instead just posing a question. This is a very bad diagram to present my lack of understanding

Because I can never take the battery out, and I have no access to what the modem is doing, I can't measure if the modem is sending data while inactive and that scares me. I also can't ever even pull the battery out to be less scared about that when I am not using the phone.

I know there are such things as faraday bags but those are expensive bulky and not always reliable from what others have said.

Although I know Graphene is open-source and trust that it's good software, I don't understand if the software prevents other parts of the hardware from communicating with each other based on the firmware code for the hardware itself. It's possible someone more knowledgeable could say definitely it could or couldn't.