Square's seemingly odd decision to buy a restaurant delivery service is starting to make sense. The company has just released Caviar's first mobile app for iOS, letting you order high-quality cooking from your iPhone in eligible cities like Chicago, New York and San Francisco. You've probably seen the basic concept of a delivery app before, but there's a clever twist here. This is more like Uber for haute cuisine; you can not only check the status of your order, but follow couriers as they bring your meal. In theory, you won't be caught off-guard when your food arrives.