This is practically impossible, as Apple wouldn't allow the app to be released on the App Store, and it also wouldn't be allowed on the Play Store. There is another way of distributing the app, however that requires users to have a jailbroken or rooted device. Even though this is possible, programming such a thing would be a incredibly sophisticated process. It would be near impossible or just impossible. For now, you can use applications such as this one. All in all, it would be a big hassle and a massive headache.