I don't think it's easy to not carry a phone, nowadays. Let's say I'm meeting up with someone: I'll need to use navigation, potentially message them if I'm running late, and so on.

Then once I'm there, what do I do with the phone? Ask to put it in a separate room and hope that the microphone isn't powerful enough to pick up our conversation?

I could turn it off entirely, but what if someone needs to call me for an emergency?

For me, as a user, the easiest solution would be to have a killswitch. I understand that building it would be more work, of course :)