This person is typically oblivious to almost all stimuli around them including any carbon-based life forms, merging traffic, lights at intersections, toll booth gates, falling pianos, the cashier in front of them, the check-out line behind them, the person they've just walked in front of, the inappropriateness of their loud phone rants, or anything else involving sight, sound or smell (such as the fungus slowly growing on the mouth and ear piece of the greasy device).
Ironically, it has been shown that when placed in a room with other family members and friends, but without the cellular appliance, this person has alarmingly little to say to any of them. This time spent communicating face to face has been estimated to be a mere fraction of the corresponding period spent talking to the same people through the device, and at great and perpetual urgency.
It's your turn dumbass! STFU and write the check or run your debit. This store has gotta ban the freaking cell monkeys in checkout lines?
Hey cell monkey, your fly is open and you're standing in front of the forklift.