Pixel hardware has the capabilities to do local ai stuff. At the baremin I know its capable of auido transcribing on its own hardware.

I would look into if there's a Foss project for pixels that can run a local voice assistant. Because its just pointing at a app in the settings and making it default it shouldn't be hard to find.

The only other option I can think of is setting up a home server with the services you need and using things like davx to sync info to your phone. I know you can run a local voice assistant there no problem, but I never tinkered around enough with home assistant to understand how to get everything the way you want. It sounded like setting up a million little automations on my phone, and then also on home assistant. I have grand disillusionment I'll get around to setting it up by the end of this year but I don't think that's happening.