I mean, you know how everyone carries a phone these days? If you use your voice, it could be potentially recorded.
So… we could just use sign language. Teach everyone sign language, use that whenever you wanna say something anti-government.
Its much easier to cover up cameras (or move out of sight) than to cover up microphones. And its unlikely people would want to leave their expensive phone in another room out of sight, so teaching everyone sign language seems like a straight-forward option.
Also, bonus: its very helpful for people with hearing problems if everyone knew sign language.
Only works for face to face communication, every long distance text will still be monitored. With enough video calls done solely using sign language, you’ll also help tools to better decipher the messages.
As others pointed out, it’s security through partial obscurity, no different from talking in esperanto or lojban.