Zara, the famous spanish fashion shop has an iPhone app that is very practical and helpful. You can browse the clothes they have and if you like any product you can easily check where you can find the product you want.
Let's say i want this T-shirt. I just need to
--> click on the "info" button --> click "In-store availability" --> click the size you want to buy --> and it will show you where to find the size you want from any of the branches in your city.
- This is helpful so next time, you don't need to reach the store and get disappointed because you didn't find your size.