I created my own app based on the exchange rate system currently in use in my country. It's a personal project, and I use it every day when shopping or doing calculations to get a rough idea of how much I'm actually spending. Hopefully, I'll save some money, of course, but I've been adding more features, such as an expense and service calculator, especially for entrepreneurs, and of course the option to make purchases with lists and so on. Little by little, I'll be changing and adding much more.