I would like to introduce you to CrysOS ROM. This project is a custom ROM, AOSP based, with all (almost) base apps, you can find in the aosp, self made. I don’t know how much this will cost, but I’d like to finish this project, so basically I don’t care how much time will I spend on it.
U4S is an android application i made to help boy scouts to manage their moneys and inventory, it’s a very simple application, controversely to what it can look like it’s functional, all data is managed by a SQLite DataBase, that each time the user clicks the respective button, it stores/deletes data from the database.
That is an open-source app, as so, my sources can be found on github: