I have one that I'm making open source, as a digital montage system.. think of the "memories" feature on Google photos or iCloud.
I basically want that to be open and free. I'll have an app to easily create albums, and have the ability to connect to any storage or montage service you like. You could even make your own app connect to your own storage and montage service, so it can be completely diy. I have a few write-ups but I'm transferring it to notion at the moment so I won't link it just yet.
My other idea is a "bill hamper / consolidation" service, that I'm doing for my sister. She pays me a flat fee each week and I pay all of her bills for her. Gives her peace of mind and allows her to save some money without stressing on paying random bills