With phone, the way it currently works (Apple, Google essentially have full control over it, the modem cpu also is closed source and has full control over appli

With phone, the way it currently works (Apple, Google essentially have full control over it, the modem cpu also is closed source and has full control over application cpu) it's not hard and people are concerned about it. With laptop (at least non mac) is a bit harder, different hardware, different OSes. Some laptops have privacy switches. Regarding turning speakers into a microphone this is possible, but turning D/A to A/D converter is much harder.