I have been working on a note taking app with a fully open API since 2008 on and off. I intended to open it to the public around 2010 but SimpleNote popped up and drank my milkshake. I even switched over myself.
Since then however they've closed their formerly open API. This inspired me to pick it back up.
I've got a mobile friendly webapp, an official SDK, a basic cli for scripting. Basically everything I wanted.
The UI of the webapp is pretty spartan as I prefer, so I'm scared it doesn't have mass appeal. It's super fast however.
I have hundreds of notes in it, use it for all my note keeping. I am it's only user. My friends have access, but they don't use regularly.
I want to open up to the public eventually, but these days I'd really want to get e2e encryption working before doing so and just have not found the time.