To explain the typical workflow here, the restaurant receives a fax from the marketplace with a phone number to call to acknowledge the delivery. There is a short numeric code on the fax print out that the restaurant types into the IVR system.

This is how these marketplaces can confirm someone is there to actually receive the order and provide that feedback to the customer that their order has been received.

I think (but am not sure) that they can provide time estimates through the IVR system as well.