iOS: Google's updated its Maps app with the addition of food ordering options. Now, when you pull up a restaurant in Google Maps, you'll see what, if any, third-party delivery services they use. You'll now see a "Place an Order" option on a number of restaurants, with links to food delivery services. When you tap the link, you're taken straight to the app itself to order food. The same goes for results on Google itself in Safari as well.
Google Maps (Free) [iTunes App Store]