My favorite app is my second mainstay App: 30/30
30/30 is nothing more than a taskmaster. It only does one thing, but it does it very well.
At the beginning of the day you create your agenda and assign each task the amount of time it should take to finish it. 30/30 will then countdown and remind you when you’ve hit your time limit. But instead of needing any action from you, it will instantly move onto the next task.
If you didn’t complete your task the first time around, it will come back through after you work through the rest of your agenda.
Again, not flashy, but it is productive.