I have an app which can be categorised as “utility” app. Due to the nature of the utility it doesn’t need connecting to a server. So, essentially, the app can be used completely offline.

Now, if I were to introduce payments into this app – what are the steps that I should be following? I am guessing there needs to be someway to track that the person has made a payment so that if the person uninstalls and install the app he/she can still continue using the paid version of the app. So, is my only option to have a server side that maintains the state of the user and thus making the app an “online” app?