Consumers in a hurry often avoid restaurants where they’ve experienced a long wait when paying their bill. Consider the number of steps it takes to pay in the traditional manner: a server presents the bill, leaves to perform other tasks while the consumer reviews it, returns after some time to take the payment to a register, settles the transaction, then returns with change or a receipt to be signed. At this point, the consumer still has to calculate a tip. Meanwhile, the table doesn’t turn....