A WiFi-only cellphone with Ubuntu, Cyanogenmod, FirefoxOS or Sailfish as an OS along with a mobile hotspot device that provides a WiFi access point might be able to get around this issue of the baseband modem having access to your CPU and memory [1].
Correct - by using two separate devices you can cheaply get around the issue today. This gets you a setup that I could agree to be trustworthy and privacy respecting.
The convenience of one device is a big sell though, plus I think a device with a built in cellular modem is more fairly called a "phone".
The convenience of one device is a big sell though, plus I think a device with a built in cellular modem is more fairly called a "phone".