Amazon tracks the gps on the phones of the couriers. The ones closest to the Whole Foods when an order comes in will get the job. Some couriers dont want to.wait near the Whole Foods all day so they hang a phone with the courier app in a tree near the store, then when an order comes in the phone in the tree forwards the order to their real phone
They are trying to game the system.
Once an order is assigned, another driver comes up and syncs their phone with the one hanging in the tree so they can take the next order. Some groups use multiple phones to keep from getting discovered. It's a slight bug in Amazon's app that supports dual screen phones & tablets (or multi-app displays) that is the core of how this all works.
My son in law was doing this for a while in Bellevue (Seattle area). He figured out that being close meant getting the best orders. He made decent money while he was doing it - like $500 a day.
How long does a phone hold a charge?