An SMS, email, or even physical mail only agent would be pretty interesting. With the socially accepted inherent limitations (text only, async, some level of misinterpretation expected) of those interfaces I'd wager it'd be possible to convincingly jump the uncanny valley today. Forcing to a comms path that's not just real-time chat affords a little more suspension of disbelief.

Particularly with growing token counts, you can have a pen pal, virtual colleague, or friend to bounce ideas off, return to previous thoughts, and chat to in cases where a real one may not exist or be available. A little ELIZA-esque, but adaptable to different needs.

My only concern is this would be be primed for misuse by people already experiencing isolation to further retreat miss opportunity to grow real social connections. Also, any semblance of privacy over those mediums would be a nightmare.