At one point, I think people did this crossing the Bay Bridge in SF. It didn't need a VC-funded startup with a bunch of expensive engineers though. I think people just parked in a known location and people pooled.
I remember there being signs on Spear St at Folsom with specific destinations for carpools. I can see them on Google Street View in 2021, but they appear to be removed in 2022. (or maybe they're designated on the paper you can't read on street view right now?)
Never had a need myself but a friend in the East Bay way back when mentioned to me once.