What's that? An app? I see a Chinese app of that name in the android play store, but it only has about 1k downloads

Only for iPhone at the moment

https://apps.apple.com/us/app/tesla-robotaxi/id6744257048

The Tesla service is colloquially called "Robotaxi".

Not just colloquially but officially...

https://www.tesla.com/robotaxi

How much per mile? For some recent example rides, let's say. One I took was exactly $2 / mile but not in SF.

For now...

Not sure why you're downvoted. I've tried Robotaxi a few times and has been great. They still have a safety driver these days and wait time is a big high though.