In order to have IO Phone call your delivery driver, you can build a filter to find leads that the delivery driver is currently active on. You'll see in the filter below, we are looking at the Shift Dates field which includes times as well. We are saying that we want any leads with shifts that are currently active by setting it as Last X Hours = 0. We can then also key off the name of the worker. We can't just set it to the delivery driver unfortunately because this filter then needs attached to a specific worker so we are not ringing all delivery drivers' phones.
The next step is to build a ring schedule that has this filter on it, no schedule settings, and have it set to ring the worker we used in the filter above. For information on setting a ring schedule, you can see the Ring Schedule article.