Store Easy Data

Project idea - those situations where youre in an area that provides no coverage (reception), or when you've physically run out of data, or when your phone services have been barred (perhaps from an unpaid bill). I want this app to have the ability to store internet data so it's essentially a backup application. For example. If a consumer usually gets 3GB of data per month on whatever phone package they get, I want the phone app to have the option to store 50mb-500mb, or more, so when the consumer has entered a no coverage zone, they can open the app and have data at their disposal. And they would be able to use the internet as normal if they were in a coverage zone. Not sure if this is even possible. Let me know fellow freelancers.