the only app that does this well for me is Todoist, but that's for tracking todos. Works via desktop app (+ global hotkey to add a todo at any time), browser (+ extension for saving webpages), mobile app, and siri (when I'm in the car). Without all those things no app has stuck for me. Todoist works decently well for short memo-type notes (you can add comments and attach files to todos), but I'm also looking for another companion app to use for more longform / wide reaching information.