Have shared this here before An inventory management software/app - for household goods, clothes even groceries You can keep track of things too old, expired, not used, can gift etc - possibly keep the stock to minimum and only for plausible usage.
Stems from minimalism, but can simply be inventory management
How does it differ from spreadsheet or a notion? Apart from reminders and stuff.
Virtual productivity pet dog app, which will help you quit phone addiction.
Fashion suggestion app: Users take pictures of themselves, app extracts their characteristics, chooses best colors, types of clothes for each season according to their characteristics, and finds similar products online for them to purchase.
I have next to 0 fashion sense and would definitely like something likr this. But I can't build this startup because, well, I have next to 0 fashion sense.