I don't quite get how that would work. They were completing tasks to train models but via sms? Can you elaborate?

There's two seperate things DoorDash seems to be doing: "Tasks" in the physical world (taking photos of inventory on shelves, closing Waymo doors), and then some seperate app for training AI models.

As for Magic, they were an SMS-based virtual assistant. They still exist today. They went downhill. https://getmagic.com/

See also https://news.ycombinator.com/item?id=34148402

https://www.ycombinator.com/companies/magic

It is a VA firm.