Sometimes when you dine in restaurants and you have an appointment or something important to do after eating your food and want to leave, the servers will not notice you are asking for the bill because the place is crowded. If the NFC, Bluetooth, WiFi technology were utilized to link the customer to his or her bill at the restaurant and the bill is paid electronically; the customer can leave when he or she wants.
This can be done by given the customer a table number and synchronized with the billing system with authorization code; then pay the bill by the accepted methods [credit cards, debit cards, Apple Cash, PayPal, or leave the cash on the table and leave]. You might do not know the total charge of your bill.
If the payment was electronically, you should receive a confirmation of the payment. If it was cash; in case of lawsuit a recording of the video surveillance is required and shows your payment.