privacy

The level of involvement here is going to largely depend on the vehicle and how many sensors/cameras and other crap the manufacturer shoved in the car. Something like a Tesla? The only viable way forward is to hack the onboard computers that collect and report the data, there's just too many codependent systems.

Most other cars, the only cameras installed are ones that you can access, like reverse cameras, plus maybe one for Lane keep or something? Which isn't facing the cabin, the only risk there is that someone will know that you're driving on a road, and maybe get your location if they're really good at Geo guesser, they get lucky with a road sign, or they have GPS info (which is more likely). Microphones, as far as I know the only cabin mic in most cars is for handsfree operation of phones and whatnot... Disabling that would ruin that functionality.

I'm sure there are cars that are more invasive on these fronts, but I dunno how much I'd want to bark up that tree.

For sensors, stuff like seat pressure sensors actually ties into SRS safety systems, so I'm not sure I'd want to mess with that. It could disable the passenger side airbag if the pressure switch is disabled... The driver side basically can't be disabled, the car doesn't go if there's no driver, so even if the pressure switch is there and disabled, the SRS should still function. Belt sensors (to tell if the belts are fastened) all tie in here too.

A lot of the external sensors are either for adaptive cruise, driver awareness, or safety systems (like crash detection for SRS).

I'm just not sure going and unplugging a bunch of sensors is the way to go.

I would assume that the data collection would come from the CANbus, so it can operate without interfering with the functions of the car, or from the BCM/ECU or other various computers around the car directly.

If the monitoring device is independent of other systems, either remove it, or sabotage the connection between it and the CANbus. Should cover most of the data being collected.