Honestly, having an app like this just adds another thing to stay on top of and keep updated (which adds to the feeling of being overwhelmed). Very few digital organizers work better than me simply making notes (in a notebook or my notes app).

The timer for a task would stress me out and make me feel rushed to finish a task. Sometimes a task takes longer than anticipated, sometimes it takes less time. It is what it is, but you can't rush. And having a countdown would absolutely make me rush.

It generally feels like a useless app that people could use to make them feel better about what they do rather than actually helping them get things done.

More discipline, less motivation. But this is just my opinion — I find it pretty easy to stick to a routine somewhat.