Using SMS/Text messages would be great idea if they were reliable. There are no delivery guarantees or confirmation of delivery. You will be upset when your car

Using SMS/Text messages would be great idea if they were reliable. There are no delivery guarantees or confirmation of delivery. You will be upset when your carrier delays delivering a message for 30 minutes and your table is given someone else. A sender gets no indication a message hasn't been delayed or even delivered. Also, lets say you are on vacation in a foreign country and the only way to know when your table is ready is to get a message. Good luck with that! I've had bad experiences where ~10% of messages sent to foreign (different +NNN) mobile numbers are never received. Apple's iMessage has much better delivery properties, but it is limited to iOS to iOS.