Apps
Here are the apps I have released and/or I am currently developing which might help your daily use case:
Monty
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A monthly subscription calculator in which you can select many currencies worldwide. Just log in with your google account and start calculating.
Currency exchange rate information is extracted from fixer.io and is updated daily.
Keep in mind that I keep your email information for identifying the owner of each subscription list.
Summer
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Source
An app to manage BOM lists. Originally meant for calculating the price of my PC build, but it can practically be used for anything. Data you have entered here persists in your browser storage so it won't be lost until you clean your browser data or uninstall your browser.
Currently only supports IDR currency. Changing currency and import/exporting files is on the roadmap.