I’m curious what movie you’re referring to? Even in Her, Theo just puts his phone in his shirt pocket with the camera exposed so Samantha can see things.
Star Trek (TNG, but the other shows too) had badges they wore on their shirts as communicators. Helped for story telling, because as opposed to a phone, the com badge would play the other person’s audio loud for all to hear.
Correct me if I'm wrong GO, but I'm pretty sure he's referring to StarTrek, by comparing this pin to a combadge.