Haha, that's great! Like a barcode reader at a UPS facility.
1) All the sushi is going around on the belt.
2) You enter your choices on your touchscreen station.
3) When one of your choices is approaching, a flapper engages and kicks it off the main belt and onto your table. The rest of the sushi keeps flowing by.
4) If you select an item that's not currently on the belt, the chefs get automatically notified. Also if the total current demand for that item exceeds total current inventory on the belt.