In the "Shared Shopping List" app you have the option to create a shopping list and share more users in the list, each of you is given the option to change the list and all this is updated in real time.
A person can sit at home and make a list, and in a few moments another person gets the list and knows what he needs to buy. Simple and convenient.
You can enter the "Shared Shopping List" page on Facebook for questions and updates.