Email definitely, just have to remember to fine tune so it says "sure, I'll get on that after lunch" rather than "as a language model…".
Voice calls, yes: I attended a talk last summer where someone did that with an AI trained on their own voice so they didn't have to waste time on whatsapp voice messages. The interlocutors not only didn't notice, they actively didn't believe it was AI when he told them (until he showed them the details).
Video… I don't think so? But that's due to latency and speed, and I'm basing my doubt on diffusion models which may be the wrong tool for the job.
