I think they should use iPads in place of menus.
There could be pictures of all the menu items to easily scroll through (like with the ebay app or the periodic table app), and if you click on an item then it would display a new page with just that item, maybe a bigger picture or animation, along with all the options and prices for that item. If someone wants that item they can then select it from that screen. When the order is ready, they just click "submit" and it goes to the kitchen over Wifi.
Then while waiting for food you can also use it to browse the web, play games, etc.
They can attach tracking devices and alarms to the iPads to make sure they don't walk out the door.